Episode Guide :: Season 6
|#||Episode Title||Original Air Date||User Rating|
|601||The Date Night Variable||September 27, 2012||4.5|
|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.|
|602||The Decoupling Fluctuation||October 4, 2012||4.3|
|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.|
|603||The Higgs Boson Observation||October 11, 2012||4.7|
|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.|
|604||The Re-Entry Minimization||October 18, 2012||4.5|
|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.|
|605||The Holographic Excitation||October 25, 2012||4.7|
|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.|
|606||The Extract Obliteration||November 1, 2012||4.4|
|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.|
|607||The Habitation Configuration||November 8, 2012||4.6|
|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.|
|608||The 43 Peculiarity||November 15, 2012||4.7|
|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.|
|609||The Parking Spot Escalation||November 29, 2012||4.7|
|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.|
|610||The Fish Guts Displacement||December 6, 2012||4.4|
|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.|
|611||The Santa Simulation||December 13, 2012||4.4|
|While the guys play Dungeons and Dragons and Sheldon is haunted by the memories of Christmas past, Raj joins the girls for ladies' night.|
|612||The Egg Salad Equivalency||January 3, 2013||4.5|
|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.|
|613||The Bakersfield Expedition||January 10, 2013||4.6|
|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.|
|614||The Cooper/Kripke Inversion||January 31, 2013||4.5|
|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.|
|615||The Spoiler Alert Segmentation||February 7, 2013||4.5|
|When Sheldon spoils a book for Leonard, he moves in with Penny. Meanwhile, when Howard and Bernadette spend a weekend in Vegas, Raj stays with Mrs. Wolowitz.|
|616||The Tangible Affection Proof||February 14, 2013||4.3|
|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.|
|617||The Monster Isolation||February 21, 2013||4.2|
|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.|
|618||The Contractual Obligation Implementation||March 7, 2013||4.5|
|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.|
|619||The Closet Reconfiguration||March 14, 2013||4.6|
|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.|
|620||The Tenure Turbulence||April 4, 2013||4.6|
|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.|
|621||The Closure Alternative||April 25, 2013||4.7|
|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.|
|622||The Proton Resurgence||May 2, 2013||4.7|
|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.|
|623||The Love Spell Potential||May 9, 2013||4.4|
|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|
|624||The Bon Voyage Reaction||May 16, 2013||4.3|
|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.|
The Big Bang Theory's sixth season sees Howard return from space and adjust to normal, married life on earth. Sheldon and Amy's unique relationship continues to progress, though at a slower pace than Amy wants. Leonard and Penny's relationship is business as usual, with Leonard once again proposing to Penny. Meanwhile, Raj finally meets a girl and enters a (somewhat) stable relationship, the demise of which leads to unexpected progress for Raj.
The season starts with Howard still in space, where he must figure out how to break the news to his mother that he'll be moving in with Bernadette. When Howard returns from space, he must adjust not only to married life but life back as a civilian. Initially, he struggles to move on from his space mission, bringing it up at every opportunity, as he fears it's the last great thing he will ever do.
Penny is unsure of her feelings for Leonard and briefly considers breaking up with him, though his sad puppy dogs and the intervention of a concerned Sheldon keep her in the relationship for now. As the season progresses, Leonard once again proposes and forces Penny to confront her commitment issues. Penny admits she's happy in the relationship and it's the inevitability of them getting married that scares her. Leonard tells Penny that he won't propose again and puts the ball in her court. At the end of the season, Leonard is offered the chance to go on a four month expedition to the North Sea. Though he worries about his relationship with Penny, she tells him to go on the expedition. Leonard leaves with their relationship seeming secure.
Sheldon and Amy's relationship progresses throughout the sixth season as Sheldon becomes more comfortable being in a committed relationship with Amy. When Sheldon ruins date night by inviting Raj, Amy demands a heartfelt statement of how he feels about her. Sheldon recites romantic dialogue from first Spider Man movie, which Amy says she'll take. When Amy comes down with the flu, Sheldon takes care of her. Hoping to enjoy more of Sheldon's caring side, Amy continues to pretend to be sick. After taking a cheek swab, Sheldon realizes Amy is no longer sick and, to punish her, spanks her.
When Sheldon starts lying to Barry Kripke about Amy and his sex life, Penny asks Sheldon whether he would consider having a sexual relationship with Amy. Sheldon admits he's always been uncomfortable with the sort of physical contact that comes easily to others, but says he's working on it and that it's a possibility. For Valentine's Day, Sheldon makes Amy his "In Case of Emergency" contact at the university. As the gang play Dungeons and Dragons, Amy gets upset at the group's mocking of their relationship. Amy asks Sheldon if he thinks their relationship will ever get intimate. Sheldon tells Amy he doesn't consider their relationship a joke and that he would not rule intimacy out. Sheldon then plays out the love potion scenario of the game with Amy, much to her pleasure.
After meeting at the Comic Book store, Raj starts dating Lucy. Lucy's social anxiety leads her to abandon Raj a number of times, causing him to get depressed. When Raj pushes her too hard, she dumps him leaving Raj devastated. When Penny visits Raj to check on him, Raj is unexpectedly able to talk to her without alcohol.
The Big Bang Theory's sixth season contained twenty-four episodes which aired between September 26, 2012 and May 16, 2013. During the sixth season, the show hit twenty million viewers for the first time. The Big Bang Theory averaged 18.68 million viewers during the season and was the 3rd highest-rated program on TV.