Episode Tournament: Nominations Round
We are running an episode tournament to find the fans' favorite episodes of The Big Bang Theory.
You can select up to 16 episodes from the left-hand pane to nominate. If you need a reminder of an episode, click the information icon for a synopsis of the episode.
Leonard and Sheldon meet their new neighbor Penny. Leonard is instantly smitten with her, but Sheldon feels he's chasing an impossible dream.
Leonard hopes to make a good impression with Penny by volunteering to sign for a package of hers. When Leonard and Sheldon move the package to her apartment, Sheldon is disturbed by her apparent lack of tidiness.
Leonard's hopes of a relationship with Penny are dashed when he sees her kiss another guy, so he decides to ask his colleague Leslie Winkle out.
When Sheldon is fired, his life descends into a series of bizarre obsessions, including "fixing" eggs and weaving ponchos. A concerned Leonard decides there's only one person who can bring Sheldon back from the brink: his mother.
Leonard is seduced by Leslie Winkle but she only wants a one night stand. Leonard is concerned his dalliance with Leslie will affect his chances with Penny.
The whole gang attends Penny's Halloween party, where Leonard's feelings for Penny come to the fore when her ex-boyfriend Kurt shows up. Leonard's attempts to impress Penny by standing up to Kurt lead to humiliation for Leonard.
Penny's promiscuous friend from Nebraska is in town and Wolowitz quickly seduces her, taking over Penny's apartment in the process. Penny takes refuge on Sheldon and Leonard's couch. With Wolowitz otherwise engaged, the guys enlist Penny as the fourth member of their Halo team.
When Raj is set up on a blind date by his parents, he worries he won't be able to talk to his date. Meanwhile, Penny practices her bar tending skills, resulting in the discovery that Raj can talk to women with the help of alcohol.
When Sheldon and Leonard are asked to present their work at a physics conference, Sheldon unilaterally decides not to. Leonard and Sheldon feud when Leonard decides to present their work alone in spite of Sheldon's objections. Penny's attempts at reconciling the pair only make matters worse.
When Leonard lies to Penny to avoid having to see her perform in a musical, Sheldon becomes concerned with the flimsiness of Leonard's lie. Sheldon constructs a much more elaborate lie which leads to the appearance of a fictional cousin.
When Sheldon catches the flu, Leonard flees the apartment to avoid having to care for a needy Sheldon. After Sheldon turns up at the Cheesecake Factory, Penny is left to care of him.
Sheldon is rattled when a 15-year-old physics prodigy, Dennis Kim, visits the university. Sheldon loses faith in his own work in the presence of the boy genius, so he decides to leave theoretical physics behind and focus on obtaining the Nobel Peace Prize. Concerned by Sheldon's career turn, the guys seek to derail Dennis Kim's progress.
The guys enter the college's Physics Bowl tournament, but Sheldon's inability to be a team player gets him thrown off the team. Sheldon decides to enter his own team, while the guys recruit Sheldon's nemesis, Leslie Winkle.
Leonard accidentally buys a full size time machine prop from the classic 1960s movie "The Time Machine". As the guys are transporting the machine to their apartment, they inconvenience Penny, who criticizes Leonard and his geeky interests.
Sheldon's attractive twin sister, Missy, is in town and the guys can't avoid hitting on her. As they all vie for Missy's affections, Leonard devises a plan to eliminate his rivals. Eventually, Sheldon decides he should determine who can date his sister. Meanwhile, Raj takes part in a drug trial to try overcome his selective mutism.
When Penny finds out that Leonard has never celebrated his birthday, she sets out to throw him a surprise party. However, a quick trip to an electronics store with Sheldon for a birthday present takes longer than she expected, forcing Howard to take drastic action to stall Leonard.
When Penny breaks up with her boyfriend after he posts intimate details about their relationship on his blog, Leonard tries to comfort her but inadvertently convinces her to get back with her ex-boyfriend. When it turns out her boyfriend has already moved on, Penny is angry at Leonard for his bad advice. Later, Leonard asks Penny out on a date and she says yes. Leonard and Penny each turn to Sheldon for romantic advice.
When her first date with Leonard doesn't go to plan, Penny confides in Sheldon, who immediately freaks out about keeping a secret.
After Leonard sees Penny with a handsome new mate, he starts up a relationship with Leslie Winkle. Meanwhile, Sheldon is unhappy with the presence of his mortal enemy in his apartment.
Sheldon and Penny bond when Sheldon introduces to her online gaming, but Penny soon finds herself addicted to the virtual world.
When Raj is featured in People's "30 under 30 to watch", the news goes to his head and makes him obnoxious to his friends.
When the gang grows tired of chauffeuring Sheldon around, they hold an intervention to make him learn to drive.
When a young grad student falls for Sheldon, the gang is confused - nobody more so than Sheldon. Though Sheldon is initially pleased to be the subject of someone's adoration, he's soon searching for ways to end their "relationship".
War breaks out between Penny and Sheldon after Penny's trivial infractions lead Sheldon to ban her from the apartment.
A smitten Wolowitz thinks he has found the love of his life, until she finds herself more interested in Leonard.
Leonard finally has a girlfriend that not only satisfies him, but also meets Sheldon's demanding standards for Leonard's cohorts.
When Leonard stumbles onto the realization that Stephanie has moved in with him, he fears their relationship is moving too fast for him and turns to Penny for advice.
It's a stressful Christmas for Leonard when his handsome colleague starts dating Penny. Meanwhile, Sheldon's obsessive gift-giving etiquette irritates the whole gang.
The guys are entering the enter the local killer robot contest but their plan goes awry when they lose their engineer, Howard, after Penny's comment about his love life sends him into a funk.
When Sheldon wants to use the university's grid computer, he decides to befriend the guy who controls access. Not well versed in the art of making friends, Sheldon develops a friendship algorithm to win over Kripke.
When Penny faces financial problems, Sheldon is happy to lend her some money. After Penny starts to regret being indebted to Sheldon, the guys are roped into a confrontation with Penny's ex-boyfriend Kurt.
A visit from Leonard's mother, Dr. Beverly Hofstadter, brings misery for the gang, except for Sheldon who is enamored with Leonard's analytical mother.
Sheldon's world is turned upside down when Penny damages his "spot" by accidentally shooting a paintball gun at his prized couch cushion. Meanwhile, Wolowitz and Leslie Winkle start dating after a paintballing encounter of their own.
When the guys take a trip to San Francisco, they're stunned to discover Summer Glau is a passenger on the train. Meanwhile, Sheldon is distraught when he realizes he left an important flash drive at home.
After Penny has an idea for a home business, she soon regrets asking for Sheldon's help when takes over the operation. The whole gang ends up spending the night trying to ship an order of a thousand Penny blossoms.
Penny is no longer the only girl in town when an attractive actress moves into the apartment building and threatens to become the "new Penny".
When Penny accompanies the guys to the comic book store, she is charmed by store owner Stuart. Leonard wonders why Penny has fallen for a guy who is just as geeky as he is.
When Howard is dumped by Leslie Winkle, Leonard and Koothrappali take Wolowitz to Las Vegas. Back in Pasadena, Sheldon is forced to spend the night with Penny.
After Howard designs a special toilet for the International Space Station, the guys rush to develop a fix to stop the toilet malfunctioning in space. Meanwhile, Penny goes out on a second date with Stuart from the comic book store.
When Sheldon is offered the opportunity to research at the North Pole, he invites the guys along with him. The impending expedition forces Penny & Leonard to reconsider their feelings for each other.
After the gang return from their Arctic expedition, Sheldon is stunned to learn that the guys manipulated his data. Fearing his reputation has been ruined, Sheldon retreats to Texas, where the guys must go get him.
Leonard and Penny's relationship hits a snag after an awkward first night together. Meanwhile, Sheldon and Howard go to great lengths to determine the species of a cricket for a bet they made.
Howard and Raj try to meet women at a Goth nightclub. Meanwhile, Sheldon attempts to build a better Penny by training her with chocolate-based positive reinforcement for what he considers her bad qualities.
When Raj faces the threat of deportation if he doesn't find a job, he must turn to Sheldon for help. Meanwhile, the newly coupled Leonard and Penny are stuck with Howard as a third wheel.
When Raj and Sheldon enter a tournament at the comic book store, Sheldon gets the opportunity to settle a score with his nemesis, Wil Wheaton. Meanwhile, Wolowitz calls on a pact with Leonard for Penny to set him up with one of her friends.
When Leonard wants to bond with Penny's football-watching friends, he turns to an unlikely source of football knowledge. Meanwhile, Howard and Raj's friendship is on the line after a kite-fighting incident.
When Penny invites an old boyfriend to stay at her apartment for a weeks, it sparks an argument between her and Leonard. Their fighting makes Sheldon uncomfortable as it reminds him of his parents' arguments.
Leonard, Howard and Raj go away on a camping trip in the desert. Back home, Penny must rely on Sheldon when she suffers an injury.
Sheldon vows revenge on Kripke after he pulls an embarrassing prank on Sheldon while he's on national radio. Meanwhile, Howard tries to keep his new relationship with Bernadette going.
When Penny wants to learn more about Leonard's work, she turns to Sheldon for lessons. Meanwhile, Howard is jealous when his girlfriend Bernadette also shows an interest in Leonard's work.
Leonard's mother, Dr. Beverly Hofstadter, visits for Christmas. His mother's visit is distressing for Leonard, especially when she finds out about his relationship with Penny, but not for Sheldon, who appreciates her analytical thinking.
Raj enlists Sheldon as his wingman when they attend a university mixer together. Meanwhile, Leonard and Penny have an argument when he ridicules her belief in psychics.
After their apartment is robbed, Leonard and Sheldon get Howard and Raj to install a complex security system. When Sheldon still doesn't feel safe, he decides to leave Pasadena.
When Sheldon struggles with a physics problem, he decides to free his mind by taking a menial job, so he starts work at the Cheesecake Factory with Penny.
When Leonard gets the opportunity to visit CERN's Large Hadron Collider in Switzerland, he must decide who to take with him as he's only allowed one guest. Leonard plans on taking Penny but faces immense pressure from Sheldon to take him.
Sheldon and the guys are excited to learn comic book legend Stan Lee will be holding a signing session at the comic book store. However, Sheldon's happiness soon fades when he gets a summons to attend traffic court.
The guys friendship is under threat when they find an authentic ring from "The Lord of the Rings" at a garage sale.
When Sheldon receives an award, his fear of public speaking threatens to derail his achievement, so the gang tries to help him overcome his fears.
Sheldon has a second encounter with his mortal enemy Wil Wheaton, this time at a bowling alley. Meanwhile, Leonard and Penny's relationship is at risk after a fight.
Sheldon is caught in the middle when Leonard and Penny, fresh from their break-up, aren't speaking to each other.
Sheldon invites a noted female physicist to stay at the apartment. While Sheldon is only interested in her mind, she garners a different kind of attention from the rest of the guys.
After a disagreement with Sheldon, Leonard tells Penny the story of how he moved into the apartment and became friends with Sheldon.
After Penny grows tired of her dim-witted date, she worries that dating Leonard has ruined her for dating normal guys. Meanwhile, Wolowitz and Koothrappali conspire to find Sheldon's perfect match online.
When Penny urges Sheldon to go on his first date, she finds herself dragged along to watch. Meanwhile, Howard finds himself in an uncomfortable position when he discovers a new use for a robotic arm.
After Sheldon worries he won't live long enough to download his conciousness into a robot, he starts making changes to extend his life.
Sheldon and Amy break up after an argument over the importance of their respective fields. Sheldon struggles to cope with the change and seeks an alternative to human companionship.
Howard is embarrassed when the reason behind his break-up with Bernadette is revealed. Meanwhile, Sheldon and Raj engage in a small war at work.
When Leonard realizes he's the only one without a girlfriend, he asks Howard to set him up with one of Bernadette's friends. Meanwhile, Sheldon is trying to lose his girlfriend after she asked him to meet her mother.
Leonard starts an affair with Raj's sister, Priya, but keeps it secret from the rest of the gang. When Sheldon gets involved, he concocts an elaborate lie.
When Howard needs top-level security clearance for a DoD project, his friends are interviewed by an FBI agent but one of their interviews puts Howard's job prospects in danger.
The guys camp out to attend a screening of Raiders of the Lost Ark featuring 21 seconds of never-before-seen footage. Meanwhile, Penny hosts a slumber party with Bernadette and Amy.
When Penny's dad visits, she asks Leonard to lie to him and pretend they're still in a relationship. Meanwhile, Howard, Raj and Bernadette spend the night monitoring a telescope in the astrophysics lab.
Amy experiences an unusual sensation in the company of Penny's ex, Zack. Meanwhile, Howard and Raj battle to find out who is the superhero and who is the sidekick in their friendship.
With New Year's Eve approaching, the guys invite Zack and Penny to join their Justice League group at the comic book store's annual costume party. Could this be the year they finally win?
When Leonard has an idea for a smartphone app, the gang get to work on developing it. Sheldon and Leonard's friendship is threatened when Sheldon tries to take over the project.
The entire gang travels to a hotel for a science conference. Their visit turns tense when Bernadette runs into her ex-boyfriend.
Sheldon is inundated with negative feedback when he teaches a class. To improve his communication skills, Sheldon gets acting lessons from Penny. Meanwhile, Koothrappali has romantic daydreams about Howard's girlfriend, Bernadette.
Leonard must consider how far he's willing to go for science when a wealthy donor makes an intimate proposal.
Leonard rekindles his relationship with Raj's sister, Priya, who is back in town. Meanwhile, Howard contemplates taking his relationship with Bernadette to the next level.
When the gang start spending more time at Priya's apartment, Sheldon realizes Leonard is the center of their social group, not him. Meanwhile, Penny tries to move on after seeing Leonard in a new relationship.
When Priya feels threatened by Leonard spending time with Penny, she forces him to cut her out of his life. Meanwhile, Howard plays mind games with Sheldon by performing a magic trick the great scientist can not figure out.
After Sheldon's World of Warcraft account is hacked, the guys go on a quest to retrieve Sheldon's items and avenge Todd Zarnecki.
After a rumor spreads that Bernadette is planning to break up with Howard, Sheldon and Amy spread their own rumors as a social experiment.
After Priya inspects the roomate agreement and disputes many of Sheldon's terms, he takes refuge with the girls.
Amy and Penny recruit Bernadette as a double agent when she and Howard have dinner with Leonard and Priya. Meanwhile, Raj tries out a new medication to cure his social anxiety.
After Howard finally tells his mother he's engaged to Bernadette, she ends up in the hospital. Meanwhile, it's bad news for Leonard as Penny and Priya bond.
Bernadette receives her Ph.D., leaving Howard as the only scientist in their group who isn't a doctor. Meanwhile, Raj becomes Sheldon's new roommate after Leonard starts staying with Priya in his apartment.
The group is still reeling from the revelation about Raj and Penny, who worries that she's screwed things up with her friends. Meanwhile, Sheldon takes charge of the paintball team.
Amy is caught in the middle of an argument between Sheldon and Penny after she takes in furniture from the street. Meanwhile, Leonard tries to spice up his long-distance relationship with Priya.
Leonard gets to know Amy when he attends a wedding as her guest. Meanwhile, Howard and Bernadette spend their weekend with Mrs. Wolowitz.
Penny introduces Raj to a girl he can communicate with - albeit with help from Howard. Meanwhile, Sheldon frees up his mind by leaving trivial decisions to the roll of the dice.
Sheldon is unhappy when Leonard wants to go to a party at Wil Wheaton's house. Meanwhile, Howard is offered an out-of-this-world opportunity.
Sheldon is upset when his mother comes to town and would rather see the sights than wait on him.
Leonard and Priya's relationship is put to the test when Leonard meets a cute comic book artist. Meanwhile, Sheldon tries to get back at the guys for a Halloween prank.
When Amy's feelings are hurt after Bernadette and Penny shop for wedding dresses without her, a reluctant Sheldon must comfort her.
Leonard and Penny try hanging out together as friends, while Sheldon is forced to overcome his fear of birds.
When Stuart asks Amy out on a date, Sheldon must confront his feelings and consider where his relationship with Amy is going.
When Leonard is contacted by his high school bully, he wonders whether to meet his old tormentor. Meanwhile, in light of what Leonard's going through, Penny reevaluates her own behavior at school.
After Sheldon is dismissive of Amy's recent accomplishment, they must work through their first relationship problem as boyfriend and girlfriend. Meanwhile, Howard struggles with Bernadette's dislike of children.
Leonard and Penny might start things up again when Leonard offers Penny a spur of the moment invitation to dinner, on the 100th episode of The Big Bang Theory.
Leonard and Penny develop a way to build a stronger relationship after they get back together. Meanwhile, Raj forms a strange relationship with his phone's virtual assistant.
When Leonard grows tired of Sheldon's selfish demands, he terminates the roommate agreement and downgrades their friendship. Meanwhile, Wolowitz tries to pick his own astronaut nickname.
After Sheldon's boss forces him to use his vacation time, he decides to work at Amy's lab and discovers he may be bad at biology. Meanwhile, Howard and Bernadette deal with the issue of a pre-nuptial agreement.
Sheldon and his archnemesis Barry Kripke compete for a newly available office at the University. Meanwhile, Penny is uncomfortable with a gift from Amy.
Sheldon is thrown for a loop when his regular barber gets sick. No longer able to stick to his routine, Sheldon embraces the chaos. Meanwhile, Wolowitz struggles with his astronaut training.
Sheldon leaves Amy in the lurch when he decides to play video games with the guys instead of going with her to her aunt's birthday party.
When Penny buys Leonard and Sheldon "Star Trek" collectibles, Sheldon listens to his "Inner Spock" and breaks his toy. Meanwhile, Raj believes he's found his future wife when he asks his parents to set him on a date.
When Howard gets to work with Professor Stephen Hawking, he offers Sheldon the opportunity to meet his hero.
When Raj gets drunk at Howard's bachelor party, he reveals a little too much about Howard's past sexual encounters, causing Bernadette to reconsider their engagement.
Howard and Bernadette's wedding plans are put in jeopardy when NASA change his mission plans. Meanwhile, Penny is thrown for a loop by a comment Leonard makes in the bedroom.
Howard and Bernadette decide they want to get married before his space launch, so the gang rushes to arrange an impromptu wedding.
A lonely Raj interrupts Sheldon & Amy's and Leonard & Penny's dates. Meanwhile, Howard and his mother are arguing, even as he's 220 miles above earth in the International Space Station.
When Penny has doubts about her relationship with Leonard, Sheldon tries to convince her to stay with him. Meanwhile, at the International Space Station, the other astronauts are picking on Howard.
Amy has feelings of jealousy when Sheldon hires a young female assistant, though it seems Penny is the one who should be concerned. Meanwhile, Howard's time aboard the International Space Station is beginning to take its toll.
Howard is disappointed when his return to earth receives less fanfare than he expected. Meanwhile, it's Girls vs. Boys when Amy and Penny take on Sheldon and Leonard on game night.
While Raj helps Stuart with the annual Halloween party at the comic book store, Sheldon and Amy are divided over their couples costume. Meanwhile, Penny takes a greater interest in Leonard's work, while Howard's friends wish he'd stop banging on about space.
Penny is taking a class at the local college but is reluctant to tell Leonard. Meanwhile, Sheldon worries about his friendship with Stephen Hawking after they play an on-line game together.
Sheldon finds himself stuck in the middle of an argument between his girlfriend Amy and friend Wil Wheaton. Meanwhile, Howard struggles with moving out of his mother's house.
Howard and Raj are intrigued by where Sheldon goes every day at 2:45. Meanwhile, Leonard gets jealous when Penny invites a guy in her class over to study.
When Howard buys a new car, the university gives him Sheldon's parking spot, sparking outrage from Sheldon. An escalating war between Howard and Sheldon affects the whole gang.
When Amy comes down with the flu, she calls on Sheldon to take care of her. Meanwhile, Howard prepares for a fishing trip with his father-in-law.
While the guys play Dungeons and Dragons and Sheldon is haunted by the memories of Christmas past, Raj joins the girls for ladies' night.
When Sheldon's assistant makes a move on Leonard, his plan to focus her mind back on work lands him with a sexual harassment complaint. Meanwhile, Penny feels insecure when she learns Alex was hitting on Leonard.
The guys take a trip to Bakersfield Comic-Con dressed as "Star Trek: The Next Generation" characters, but after their trip goes off course they lose faith in their geeky interests. Meanwhile, the girls try to take an interest in comic books.
When Sheldon is forced to work with Barry Kripke, he is surprised to find his work is not as good as Barry's. Meanwhile, Howard and Raj spend $1,000 on action figures of themselves.
When Sheldon spoils a book for Leonard, he moves in with Penny. Meanwhile, as Howard and Bernadette spend a weekend in Vegas, Raj stays with Mrs. Wolowitz.
Leonard and Penny go on a double date with Howard and Bernadette on Valentine's Day, while Sheldon and Amy search for the perfect presents for each other. Meanwhile, Raj and Stuart throw a party for single people at the comic book store.
After his date walks out on him, Koothrappali withdraws from the world and hides out in his apartment. Meanwhile, Penny's acting skills impress Sheldon when he sees her in a play.
Leonard, Sheldon and Howard visit Howard's old school to talk to junior high girls about careers in science. Meanwhile, Raj plans his first proper date with Lucy, while the girls visit Disneyland.
When Sheldon reorganizes Howard's closet, he finds an unopened letter from Howard's father. Howard is torn over whether he should finally read the letter or not. Meanwhile, Leonard and Penny throw their first "grown-up" party.
When a tenured position opens up at the university, Leonard, Sheldon and Raj compete for the job. The competition intensifies when the girls get involved.
When one of Sheldon's favorite TV shows is canceled, Amy helps him work through his compulsive need for closure. Meanwhile, Raj finds his girlfriend's blog, and Penny searches for something she's passionate about.
When Sheldon discovers his childhood hero, Professor Proton - a TV science show host, is available for children's parties, Sheldon and Leonard hire him to perform for them. Meanwhile, Howard and Bernadette take care of Raj's dog.
After the girls' trip to Vegas goes awry, they join the guys for a game of Dungeons and Dragons, which takes Sheldon and Amy's relationship to an unexpected place. Meanwhile, Raj and Lucy have a very awkward date
When Leonard receives an exciting job proposal, Penny worries about their relationship, while Sheldon deals with feelings of jealousy. Meanwhile, Raj pushes too far in his relationship with Lucy.
With Leonard away at sea, Sheldon and Penny bond over their intimate secrets. Meanwhile, Raj is consoled as he deals with his break-up from Lucy, and Amy and Bernadette spend time together at a science convention.
Sheldon is distraught when Leonard returns from his expedition early but doesn't tell him. Meanwhile, Howard's close relationship with his mother causes his masculinity to be called into question.
Raj devises a scavenger hunt for the gang, but the intense competition causes friction among the friends.
When Amy points out a flaw in the plot of one of Sheldon's favorite movies, he vows revenge by ruining something she likes. Meanwhile, Leonard finds a way to manipulate Penny into doing anything for him, while Raj and Stuart set up online dating profiles.
Sheldon is afraid he'll be spending too much time with Amy when she takes up a job at his university. Meanwhile, Howard ends up sleeping on Raj's couch after a disagreement with Bernadette.
Sheldon is thrilled when he has a scientific breakthrough, but his excitement quickly turns to dread when he realizes he made a mistake. Meanwhile, Howard surprises Bernadette with a romantic gesture, leading Penny to up her game with Leonard.
When Sheldon's idol, Professor Proton, seeks Leonard's help for a science paper instead of his, Sheldon gets his revenge by befriending rival science icon Bill Nye. Meanwhile, Raj is jealous when Howard starts crashing girls' night.
When a past mistake of Leonard's comes to light, he's surprised when Sheldon promises not to make a big deal out of it, instead making Leonard walk a mile in his shoes. Meanwhile, Penny embarrasses Raj when she confronts his ex-girlfriend, Lucy.
Sheldon gripes when he is forced to spend Thanksgiving at Mrs. Wolowitz's house. Meanwhile, Penny and Leonard confront a mistake from her past.
Sheldon is comforted by Leonard and Amy when his accidental science discovery is disproved. Meanwhile, Raj stays at Howard and Bernadette's apartment for the week.
When Sheldon flies back to Texas, the gang gather to decorate the apartment Christmas tree, and they come to realize how big a part of their lives he is.
After Penny's big acting break on NCIS gets cut, Leonard's attempts to help her lead Penny to make a big relationship decision. Meanwhile, Raj tries to improve his "game" before re-entering the dating world, and Sheldon learns how to be funny.
Sheldon struggles to relax when the university forces him to use his vacation time. Meanwhile, Leonard tries to support Penny after she decides to quit her job, and Bernadette needs Stuart's help when she accidentally destroys one of Howard's comic books.
When the guys miss out on Comic-Con tickets, Sheldon plans to hold his own convention, leading to a memorable night with James Earl Jones. Meanwhile, the girls try to act like "grown-ups".
Amy surprises Sheldon with a romantic weekend that even he can't say no to: a weekend trip to Napa Valley aboard a vintage train. Meanwhile, when Leonard and Penny spend Valentine's day caring for Raj's dog, the special day ends with a journey to the vet.
When Leonard buys a new dining room table for the apartment, Sheldon begins to reconsider the changes made in his own life. Meanwhile, Howard's offered the chance to go back to space, but Bernadette doesn't think it's a good idea and doesn't know how to tell Howard.
When Howard and Sheldon get into a tiff, Bernadette tries to bring the friends back together. Meanwhile, Penny is offered an embarrassing movie part, while Raj gets Amy to contact a woman on his behalf.
When Sheldon stops by his mom's house in Texas, he must learn to deal with her new romantic status. Meanwhile, Raj throws a Murder Mystery party for the gang.
While Penny struggles to decide whether to take a role in an embarrassing movie, Sheldon is torn over which video game system to buy, and Raj is dating two women at once - but will the guilt be too much for him?
Sheldon has had enough of string theory after twenty fruitless years in the field. Meanwhile, Howard is embarrassed when Raj and his girlfriend Emily have a double date with him and Bernadette.
In a bid to be spontaneous Sheldon brings back Anything Can Happen Thursday, leading to him spending the evening with Penny after she's angered by Amy and Bernadette. Meanwhile, Raj gets Howard's advice for his upcoming date with Emily.
Professor Proton delivers Sheldon a lesson in coping with grief. Meanwhile, a reflective Leonard and Penny get competitive with proposals to change their relationship. Elsewhere, Amy and Bernadette work on a "Star Wars Day" gift for the guys.
A bad day at work causes Penny to reconsider the decisions she's made in her career - and her romantic life. Meanwhile, Howard and Bernadette take care of an injured Mrs. Wolowitz, and Raj gets relationship advice from Sheldon.
With his career in flux Sheldon struggles to deal with all the changes in his life, leading him to make a drastic decision. Meanwhile, Raj and Emily's relationship takes a step forward, while an injured Mrs. Wolowitz puts a strain of Howard and Bernadette's life.
After spending the summer riding the rails, Sheldon's cross-country train journey comes to an end in Arizona, where Leonard and Amy must drive out and pick him up. Meanwhile, Bernadette secures Penny a job interview, and Howard grows concerned about Stuart's relationship with his mother.
Sheldon gets promoted to a junior professor at the university, but he must now teach a class. When no one signs up for Sheldon's class, Howard surprisingly enlists. Meanwhile, Amy plays Penny and Bernadette against each other when tensions rise over Penny's new job at Bernadette's company.
When Wolowitz is asked by NASA to throw the first pitch at a Los Angeles Angels Game, he worries about embarrassing himself. Meanwhile, Sheldon claims that he and Amy are the "superior couple" to Leonard and Penny.
Raj's openness about his romantic history leads to tension between his girlfriend Emily and Penny. Meanwhile, the guys consider investing in Stuart's comic book store to help it reopen after the fire.
When the guys want to spend the weekend working on science projects, the girls opt for a weekend trip to Vegas. After Penny receives an email from work, Amy and Bernadette accuse her of being a buzzkill. Meanwhile, the guys' efforts to invent something cool fizzle out when they keep getting distracted.
Sheldon and Raj consider applying for a dark matter research expedition in a salt mine, but first they test their ability to survive the rough conditions by emulating the conditions in the university's steam tunnel. Meanwhile, Leonard and Penny have an argument about money and seek help from Howard and Bernadette.
A doctor misconstrues Penny's workplace flirting and falls for her. When he turns up at her apartment, he attracts the attention of the guys. Meanwhile, Bernadette is going to be featured in an article about hot female scientists, but Amy disapproves of the article.
After Penny's old prom dress brings up memories of their proms, the girls decide to recreate prom night on the roof of the apartment building. As Sheldon learns about prom customs, he worries that Amy will expect something to happen between them.
Sheldon is troubled when Leonard decides to get minor surgery on his nose. Meanwhile, Raj is distraught when he finds out his parents have divorced on the eve of their 40th wedding anniversary.
Sheldon and Amy record the final episode of "Fun with Flags". Meanwhile, Leonard, Howard and Raj are forced to consider their own contribution to science as they clear out the office of a deceased professor, and Bernadette is surprised to learn what her co-workers really think of her.
Leonard and Howard have a situation in a clean room at the university and call on Raj's help. Meanwhile, Amy hosts an authentic Victorian Christmas party, while Sheldon resents being made to celebrate the holidays.
When Penny and Amy feel Leonard and Sheldon force them to embrace their interests but never return the courtesy, the girls take Sheldon and Leonard along when they go clothes shopping. Meanwhile, Howard tries to occupy Raj, who is nervously awaiting the results of a space probe he helped launch.
When Sheldon decides his comfortable lifestyle may be holding back his scientific progress, he asks his threads to irritate and annoy him to improve his work. Meanwhile, Howard embarrasses Raj by creating a new game, 'Emily or Cinnamon?'.
When Sheldon and Leonard co-publish a physics paper online, they find themselves dealing with an unexpected Internet troll. Meanwhile, Penny, Amy and Bernadette spend girls' night finding each other's embarrassing moments.
As they prepare for the reopening of Stuart's comic book store, the gang is at each other's throats. Howard is angry at Stuart for taking furniture from his mother, while Penny and Leonard are angry with Amy and Sheldon for running experiments on them. Meanwhile, Leonard and Raj think they see Firefly star Nathan Fillion at a restaurant.
Sheldon and Penny spend the evening performing an experiment to see whether people can fall in love in a few hours. Meanwhile, Leonard, Amy, Raj and Emily visit an "escape room" where they are tormented by a zombie. Meanwhile, Howard and Bernadette encounter trouble as they fly back from Mrs. Wolowitz's funeral.
As Sheldon and Amy choose to buy a pet turtle, Amy is angered to learn that Sheldon has applied for a one-way mission to colonize Mars. Meanwhile, Leonard and Penny take a step forward in the bedroom when Leonard makes an adult purchase, while Raj worries about Emily's reaction when she finds out he's been snooping in her apartment.
Tensions rise between Sheldon and Leonard when a magazine article about their paper fails to mention Leonard. Elsewhere, when the electricity goes down at Mrs. Wolowitz's house, the gang salvage the defrosting food by throwing a final family dinner in her honor.
Sheldon and Leonard take a detour on the way to give a speech at UC Berkeley, hoping to meet an idol of theirs. Meanwhile, a disagreement between Howard and Bernadette over the future of his Doctor Who TARDIS leads to a ping pong battle with Penny, Raj and Amy.
When Sheldon feels down about being left out of a physics symposium, Amy suggests they spend their date night building a fort. Meanwhile, after Howard gets the title deed to his mother's old house, he is surprised when an unknown relative turns up on his doorstep. Meanwhile, when Penny appears on Wil Wheaton's podcast, she and Leonard have a big on-air fight.
After Raj is given the job of crafting a message for NASA in case their mission discovers alien life, the guys argue over their roles in helping Raj. Meanwhile, Penny must decide whether to audition for a movie or stay with her successful pharmaceuticals job.
Leonard is set to give the commencement address at his former high school, but a canceled flight threatens to prevent him from giving the speech. Meanwhile, Howard's engineering skills are tested as he and Sheldon attempt to fix Raj's toy helicopter, while Raj plays his parents against each other after his father cuts him off financially.
When Sheldon and Leonard receive an award for the paper they co-wrote together, their mothers pay a visit to Pasadena. Sparks fly between Mary Cooper and Beverly Hofstadter when they can't see eye to eye on religion or psychiatry. Meanwhile, Bernadette has had enough of feeling like a mother to three teenage boys, so Howard, Stuart and Raj are ordered to clean the kitchen.
After Sheldon upsets Amy on their fifth anniversary date night, they both confront the state of their relationship. Sheldon's relationship reflection pushes Leonard and Penny to reexamine their engagement.
When Penny and Leonard arrive in Vegas to get married, Penny is still thinking about Leonard's admission that he kissed another girl. Meanwhile, Sheldon doesn't know what to think after Amy calls time on their relationship.
As Leonard and Penny struggle with the revelation he kissed another woman, Leonard goes to meet the woman in question, Mandy, in a bid to show Penny there's nothing to worry about. Meanwhile, Sheldon films an episode of Fun with Flags alone following his break-up with Amy, who is angered by Sheldon's thinly veiled comments about their recent split.
When the guys head off to Mexico to throw a belated bachelor party for Leonard, their science skills are put to the test when their van gets a flat tire. Meanwhile, Bernadette and Amy pressure Penny to finally tell her parents she eloped with Leonard during her low-key bachelorette party.
When Sheldon learns that Leonard is now living with Penny, he reverts to a simpler time before he met them both. Howard and Raj form a folk sci-fi band to play live music at the Comic Book Store.
When the guys sign up for Barry Kripke's fencing class, Sheldon finds himself in an uncomfortable position when Barry expresses an interest in the now-single Amy. Meanwhile, the girls try to help Stuart attract more female customers to the Comic Book Store.
In the midst of a nation-wide helium shortage, Sheldon and Leonard take desperate measures to get the supplies they need. Also, Penny and Bernadette download a dating app on Amy's phone to try and find her a new man.
While being interviewed for a documentary about Spock from "Star Trek," Sheldon struggles to suppress his emotions about his recent break-up with Amy. Also, Wolowitz and Bernadette butt heads over remodeling his childhood home.
Sheldon, Wolowitz and Koothrappali post an online advertisement to find Sheldon a new girlfriend. Also, when Amy is coy with details about a guy she is dating, Penny and Bernadette decide to spy.
Sheldon and Amy try hanging out as friends when they spend Thanksgiving together at the aquarium. Also, Wolowitz reluctantly agrees to volunteer at the soup kitchen with Bernadette, Raj and Emily, and Penny discovers that Leonard knows more about her than she thought.
Sheldon has a revelation when he realizes why a song was stuck in his head. Also, Amy invites Dave over for dinner despite their previously awkward date, and Wolowitz and Koothrappali become obsessed with a fan of their band, "Footprints on the Moon".
After more than five years of dating, Sheldon and Amy spend their first night together. Also, Leonard, Wolowitz, and Koothrappali must decide who will take their extra Star Wars movie ticket.
Penny gets more than she bargained for when Leonard agrees to meet with a psychiatrist on her behalf. Also, Sheldon and Koothrappali collaborate on an astronomical discovery, and Wolowitz and Bernadette can't believe what they are feeling after Stuart moves out.
After having to deal with a sick Sheldon, Leonard, Penny and the gang try to treat themselves to a Sheldon-free weekend.
Sheldon's thrilled when his Meemaw comes to visit, but his excitement quickly fades when she butts heads with Amy. Also, Raj meets a new girl at the comic book store who makes him question his relationship with Emily.
Sheldon and Amy host a live Valentine's Day episode of Fun with Flags, Leonard and Penny grapple with getting older, Howard and Bernadette find a surprise in their hot tub and Raj is torn between Emily and the cute girl he met at the Comic Bookstore.
When the gang finds out about Bernadette's pregnancy, they celebrate by singing karaoke. Also, Bernadette is concerned when Wolowitz freaks out over her pregnancy announcement, and Wolowitz is convinced he must make more money to provide for the baby.
After more than nine years together, the gang finally celebrates Sheldon's birthday, surprising him with a special guest, on the 200th episode of The Big Bang Theory.
Leonard, Sheldon, and Wolowitz run into problems when they file for a patent for their infinite persistence gyroscope. Also, Penny, Amy and Bernadette give Koothrappali dating advice when Emily reaches out to him after their breakup.
Amy is shocked at a revelation from Sheldon after she buys him a new laptop. Also, Koothrappali sells out Leonard and Wolowitz after they lie to their wives in order to attend an early screening of a movie.
Sheldon spills a secret of Leonard's when the two take a weekend cabin trip with Penny and Amy. Also, when Koothrappali goes overboard with pregnancy gifts, Wolowitz and Bernadette must draw the line.
Everyone must choose sides when a small argument between Leonard and Sheldon erupts into a heated fight during a group get-together.
The gang goes to a wine bar and runs into Penny's old boyfriend, Zack. Also, Bernadette gets stuck spending the evening with Sheldon when she can't go wine tasting with the group, and things don't go as planned when Koothrappali introduces his new girlfriend, Claire.
Sheldon hires Stuart to spend the day with Amy when he'd rather go to a movie screening. Also, Leonard's mother, Beverly, comes to town and Penny struggles to make a connection with her.
Chaos ensues when Leonard's recently divorced parents, Alfred (Judd Hirsch) and Beverly (Christine Baranski), and Sheldon's devoutly religious mother, Mary (Laurie Metcalf), come to town. Also, Wolowitz and Koothrappali think the government is out to get them when they are contacted about their guidance system.
On the day of Leonard and Penny's second wedding ceremony, there's an awkward morning after for Sheldon and Leonard as they fret about how Mary and Alfred returned to their hotel together. Meanwhile, Penny's family comes to town for the wedding, but it's a stressful time for Penny's mother, Susan, who is worried about how her family will be perceived because of her son Randall's criminal history.
Howard finally meets Air Force representative Colonel Williams to discuss the guidance system project. Meanwhile, Bernadette is upset to find out that somebody at work revealed she is expecting.
When the guys work long hours to try finish their project for the military on time, Sheldon struggles to stay awake and turns to energy drinks to keep going. Meanwhile, Penny and Amy attend a party being thrown by Bert, the geologist, and Koothrappali helps Bernadette prepare the house - and herself - for the arrival of her baby.
After Amy's apartment is flooded, Penny suggests that Amy move into Apartment 4A with Sheldon. Unsure about finally cohabiting with his girlfriend, Sheldon comes around to the idea when he looks at it as a five week experiment in living together. Meanwhile, Howard and Bernadette decide not to learn the gender of their baby, but they question their decision when Raj reveals that he knows the sex of the baby.
When Sheldon and Amy start bickering over their living situation, Leonard and Penny step in to keep the pair separate and to give them advice on living with a significant other. Meanwhile, after Howard and Bernadette blow off a planned vacation, they observe a pair of unexpected guests in their hot tub.
Penny is surprised to learn she has fans of her performance in "Serial Ape-ist" when she attends Van Nuys Comic Con with Leonard. Also, Amy hosts a Sheldon-style brunch at Penny's apartment and Wolowitz makes an impulsive purchase when he starts stressing out about the baby on the way.
After Amy's apartment is ready to move back into, she lies to Sheldon about the state of the construction work so they can keep living together. Meanwhile, Leonard learns that Penny has been secretly moving his collectibles into storage.
When Sheldon and Amy successfully combine their genes and cultivate brain cells, Sheldon thinks they should go a step further and have a baby together. Meanwhile, when Raj meets a woman at work he finds himself embarrassed to tell the guys about her job at the university.
Sheldon battles with feelings of jealousy when geologist Bert wins a MacArthur Genius fellowship. Meanwhile, Howard finds an old remote control Stephen Hawking toy he made, which receives negative feedback from his friends.
Sheldon and Leonard end up in a bitter tit-for-tat fight when they try to divvy up their mutual belongings from Apartment 4A. Meanwhile, Raj and Stuart compete to be the most helpful to Bernadette in her final weeks of pregnancy.
It's Amy's birthday again, so she and Sheldon are going to enjoy their annual tradition of coitus - if the birth of Howard and Bernadette's baby doesn't interrupt them.
When the gang gets together for the first time in the New Year, they catch each other up on their holidays - including a fight over a Christmas tree, a trip to Texas, and their newborn's first few days at home.
After Penny starts to feel like Leonard is taking her for granted, she chooses to go on a spa weekend with Amy. Meanwhile, Howard and Raj think up inventive ways to try fix a squeaky floorboard in baby Halley's room.
Sheldon tries to improve his understanding of people's emotions by beta testing a new MIT invention which can detect how people are feeling. Meanwhile, Leonard and Penny argue when she wants to invite her brother to stay with them, and Raj convenes a meeting of his ex-girlfriends to try understand why they broke up with him.
When Sheldon threatens to derail their project, Leonard and Howard find a way to keep him occupied. Meanwhile, Penny and Amy enjoy a girls' night out with Bernadette, leaving Raj and Stuart to look after the baby.
When Amy finds out that Sheldon has been sharing personal details of their relationship at work, they have their first fight as a cohabiting couple. Meanwhile, Raj is hurt when his father stops trying to fix him up with somebody, claiming that Raj is too spoiled to be attractive to somebody.
After a newly cash-strapped Raj puts Sheldon in charge of his finances, he's disappointed to learn that he might not be able to afford to attend Comic-Con this year. Meanwhile, Penny decides to go with Leonard to Comic-Con this year.
When Raj can no longer afford his apartment after cutting himself off from his father's money, Leonard and Penny offer up Sheldon's old room. After Sheldon struggles to let go of his old room, he offends Raj and causes trouble in Leonard and Penny's relationship.
When Penny and Raj enjoy spending time together as roommates, Leonard starts to feel like a third wheel. Meanwhile, Sheldon's interest in Amy's work leads them to collaborate, but they soon find they can only work well together when they're at each other's throats.
When Sheldon works himself to the bone with two projects at once, he falls ill and loses track of a whole day. Meanwhile, Bernadette has mixed feelings as her maternity leave comes to an end.
Howard and Bernadette struggle to leave Halley in day care when Bernadette's maternity leave is over. Meanwhile, when Bert introduces the guys to his new girlfriend, Rebecca, they question her motives.
Fearing his great mind is letting him down, Sheldon vows to improve his cognitive function by learning new tasks. Meanwhile, Leonard isn't impressed when Penny is offered a job by her ex-boyfriend, Zack.
Howard, Leonard and Sheldon celebrate the end of their top secret Air Force project, but their happiness is short-lived. Meanwhile, Amy is offered a visiting researcher position at Princeton for the summer, but she's not sure whether to take the job.
When Sheldon's old admirer, Dr. Ramona Nowitzki, returns to the university while Amy is away at Princeton, Sheldon's friends try to protect his relationship with Amy.
Amy's answer to Sheldon's proposal is overshadowed by his need to be the center of attention. Meanwhile, Howard and Bernadette get some unexpected news.
Leonard fears for his job when he gives a downbeat assessment of the state of physics research in a national radio interview. Meanwhile, Amy and Bernadette realize they both feel they have to hide success in their careers from their significant others.
Amy tries to get Sheldon to calm down when he stresses out about picking the perfect date for their wedding. Meanwhile, Raj and Stuart both fall for Bernadette's new co-worker, Ruchi.
As Howard worries about fatherhood, he and Sheldon bond when as assemble a model rocket together. Meanwhile, Leonard is concerned when Penny starts bonding with his mother.
When Howard and Amy collaborate on a project, Sheldon and Raj struggle with feelings of jealousy and loneliness. Meanwhile, Penny and Leonard get help for dealing with Sheldon from an unlikely source.
When Sheldon learns that Professor Proton's show is being redeveloped, he decides to audition for the role and ends up in competition with Wil Wheaton. Meanwhile, Penny takes care of Halley when Howard and Bernadette are put on bed rest.
When Bert offers Sheldon the chance to work with him to research dark matter, Sheldon is ashamed to be interested in working on a geology project. Meanwhile, Raj gets advice from Penny and Bernadette when Ruchi agrees to go out on a date with him.
Leonard and Howard are angry with Sheldon when they learn he has been working with the military behind their backs. Meanwhile, Raj's relationship with Ruchi is called into question when a bed-ridden Bernadette fears she is trying to steal her job.
When Sheldon remembers mining Bitcoin a few years ago which are worth significantly more today, the guys go on a quest to track down their missing digital fortune. When they turn to Penny's ex-boyfriend Zack, Leonard is moved by an old video of Penny.
Sheldon and Amy take the stress out of wedding planning with the application of decision theory. Meanwhile, Koothrappli ends his friendship with Howard when he realizes that his best friend's put downs are harming his confidence.
As Sheldon plans a birthday celebration for Amy, Howard is looking forward to Halley's first birthday. Meanwhile, Leonard has the holiday blues when he receives a Christmas letter from his brother detailing his many accomplishments.
When Sheldon and Amy put their friends through a series of secret experiments to determine who should be their best man and maid of honor, Penny's true feelings about Amy are revealed.
After Sheldon decides to work solo without Amy, she turns to Leonard to work together on a series of science experiments. Meanwhile, geologist Bert replaces Howard in Footprints on the Moon, while Sheldon gets an unexpected source of scientific inspiration from Penny.
Raj gets caught in the middle of a domestic dispute when he learns the woman he's dating, Nell, is still married to her husband, Oliver. Meanwhile, when Sheldon rents his old room back so he has a place to focus on his work, he annoys Leonard by being the perfect tenant.
Sheldon is disappointed when he appeals to Wil Wheaton to appear on the new Professor Proton show, only for Wil to choose Amy instead. Meanwhile, Leonard is writing a novel and manages to upset Penny, who thinks a character is based on her.
When Bernadette's pregnancy drags on, her friends each try their own solution to get things moving. Meanwhile, Howard confronts Bernadette after learning she has already chosen a name for their new baby boy.
When Sheldon and Amy find the perfect place to host their wedding, Leonard is called on to make it happen. Meanwhile, Howard and Bernadette struggle to decide who should stay at home with the kids.
Penny gets the opportunity to host Bill Gates at work when his company wants to partner with her pharmaceutical company. Also, Leonard, Koothrappali and Wolowitz do everything in their power to meet him, while Sheldon thinks he is the victim of an April Fools prank.
After Leonard finds out that Sheldon is the president of the building's tenants' association, he and Penny attempt to overthrow him. When Howard and Raj find a crashed drone in the backyard, Bernadette encourages them to locate the owner.
When a reclusive genius, Dr. Wolcott, invites Sheldon to his cabin in the middle of nowhere, Leonard, Howard and Raj go along for the trip. Meanwhile, Penny and Bernadette try to spice things up when Amy finds the bachelorette party they threw her too tame.
When author Neil Gaiman gives Stuart's comic book store a popularity boost, Sheldon is uncomfortable with the changes at the Comic Center. Meanwhile, Raj takes credit for an astronomical discovery made by Penny, putting their friendship at risk.
Sheldon goes to Vegas to win money for science. Also, Penny and Bernadette take Amy wedding dress shopping, but her terrible choice entangles them in a web of lies.
When Sheldon learns that his mother won't attend his wedding unless he invites his brother, Georgie (Jerry O'Connell), he and Leonard travel to Texas to end a family feud. Also, the Wolowitz kids inadvertently infest Amy, Bernadette, Wolowitz and Koothrappali with pinkeye.
When Amy's parents and Sheldon's family arrive for the wedding, everybody is focused on making sure all goes according to plan - everyone except the bride and groom.
Sheldon's obsessive need to schedule everything leads to his and Amy's first argument as a married couple when they honeymoon in New York. Meanwhile, Leonard and Penny are disturbed to see similarities between their marriage and Amy's parents' dysfunctional relationship, and Raj gets into a Twitter feud with astrophysicist Neil deGrasse Tyson.
Sheldon and Amy struggle to figure out what the wedding gift they received from Leonard and Penny is. Meanwhile, Raj decides he's ready to settle down, and Stuart asks Denise out on a date.
Leonard and Penny don't see eye-to-eye when they discuss starting a family. Meanwhile, Howard and Bernadette's home life is disturbed when Stuart starts bringing his girlfriend back to their place, and Raj meets a woman for an arranged marriage.
When Sheldon won't tell anyone why he's never mentioned Tam, his childhood best friend, Leonard takes matters into his own hands. Also, Bernadette and Penny take out Raj’s fiancée, Anu, for dinner to get the skinny on her.
When Sheldon feels that Amy's job isn't leaving her enough time to work with him on super-asymmetry, he goes behind her back and unwittingly sabotages her career in the process. Meanwhile, Raj is unhappy at the prospect of Howard joining him in hosting a show at the planetarium.
Sheldon is offended when Howard dresses up like him for Halloween, so he and Amy get their revenge at Leonard and Penny's Halloween party. Meanwhile, Leonard is surprised that Penny doesn't remember their first kiss.
When Leonard is tasked with distributing extra grant money, he struggles with his desire to please everyone. Meanwhile, Bernadette seeks refuge in the backyard playhouse when she feels overwhelmed by work and family life.
After Sheldon realizes he should have a better relationship with Amy's parents, he sets out to bond with Mr. Fowler. Meanwhile, Raj and Anu decide to find out whether they're compatible in the bedroom before they marry.
When Sheldon and Amy ask Leonard to gather citations for their super-asymmetry paper, they are devastated when he finds a Russian paper which disproves their theory. Meanwhile, when Bernadette wants to beat Howard at Fortnite, she turns to Denise for a gaming lesson.
With Sheldon and Amy down in the dumps after their theory was disproved, Leonard retrieves an old VHS recording to cheer him up. Meanwhile, an old video of Howard as an aspiring magician leads Bernadette to act as his pageant mom and coach him for his Magic Castle audition.
Penny and Leonard organize a paintball game that results in mayhem when Sheldon is jealous of Amy. Also, Koothrappali catches Anu with her ex-boyfriend, and Stuart doesn’t want to move in with Denise.
After Penny runs into Zack at a bar, she and Leonard are invited to dinner on his boat where Zack and his wife ask them for an unusual favor. Meanwhile, Raj tries to patch things up with Anu.
Sheldon and Amy are thrilled when two physicists from Fermilab prove their theory of super asymmetry, but their joy dissipates when Doctors Pemberton and Campbell try to take credit for the work. Meanwhile, Bernadette offers Penny the chance to head up the sales team for a drug she developed.
Sheldon is thrilled to help Bernadette and Wolowitz navigate bureaucratic paperwork, until he discovers they are breaking the law. Also, Leonard is disappointed when his friends exclude him from a scientific project.
When Penny's father, Wyatt, comes to town, he reopens the debate over Penny not wanting kids and Leonard donating his sperm to Zack and Marissa. Meanwhile, Howard decides to keep the reservation for the "vomit comet" he originally made for Raj's planned bachelor party.
After Sheldon discovers that Wil Wheaton hosts a Dungeons and Dragons game for his famous friends, the guys set out to claim a seat at the table.
When Penny and Bernadette go to a pharmaceutical convention in San Diego, Howard is left in charge of the kids and allows Sheldon to perform experiments with them.
After their Nobel prize competitors, Drs. Pemberton and Campbell, go on a publicity tour, Sheldon and Amy seek support from a trio of Nobel laureates: Kip Thorne, George Smoot and Frances Arnold. Meanwhile, Bernadette has the idea of turning Howard's time as an astronaut into a children's book.
Amy feels the pressure after she is told that her winning a Nobel prize could inspire a generation of female scientists. Meanwhile, Howard buys a scooter like he used to own and tries to keep it from Bernadette.
After Leonard decides to stand up for himself and not try to please everyone all the time, he demands a new job at the university. Meanwhile, Raj worries he has become a laughing stock in his field when he publishes a paper which raises the possibility of alien life.
After Barry Kripke reveals that Dr. Pemberton plagiarized his thesis in college, Sheldon and Amy debate whether to expose the fraud. Meanwhile, Bernadette tells Howard about the worst thing she ever did to get something she wanted.
Leonard wonders what's going on when Beverly visits and shows an interest in his work. Meanwhile, Stuart and Denise consider their options when Howard and Bernadette tire of them staying at their house.
Sheldon and Amy await big news, on the series finale of The Big Bang Theory.
Bernadette and Wolowitz leave their kids for the first time; Penny and Leonard try to keep a secret; Sheldon and Amy stick together; and Koothrappali makes a new friend, as the gang travels together into an uncharted future, on the series finale of The Big Bang Theory.
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