Leonard & Penny: Key Episodes
The key moments in Leonard and Penny's relationship including the first time they saw each other across the hall, their first kiss, their first date, breaking up and getting back together, the first time Penny says "I love you", a couple of proposals, their engagement, two wedding ceremonies, and finally Penny getting pregnant.
Season 1, Episode 1 - Aired September 24, 2007
Leonard and Sheldon meet their new neighbor Penny. Leonard is instantly smitten with her, but Sheldon feels he's chasing an impossible dream. Leonard talks Sheldon into helping Penny out by retrieving her television from her ex-boyfriend Kurt.
The Fuzzy Boots Corollary
Season 1, Episode 3 - Aired October 8, 2007
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 Leslie is uninterested in going out with Leonard, he feels dejected and thinks about getting a cat. In an attempt to buoy Leonard's spirits, and stop him getting a cat, Sheldon encourages Leonard to ask Penny out on a date.
The Middle-Earth Paradigm
Season 1, Episode 6 - Aired October 29, 2007
The whole gang attends Penny's Halloween party, where Leonard's feelings for Penny come to the fore after her ex-boyfriend Kurt shows up. Leonard's attempts to impress Penny by standing up to Kurt lead to humiliation.
The Tangerine Factor
Season 1, Episode 17 - Aired May 19, 2008
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.
The Monopolar Expedition
Season 2, Episode 23 - Aired May 11, 2009
When Sheldon is offered the opportunity to conduct research at the North Pole, he invites the rest of the guys along with him. The impending three-month expedition forces Penny & Leonard to reconsider their feelings for each other.
The Electric Can Opener Fluctuation
Season 3, Episode 1 - Aired September 21, 2009
After the gang return from their Arctic expedition, Sheldon is stunned to learn that the guys manipulated his data and invalidated his research. Fearing his scientific reputation has been ruined, Sheldon retreats to his mother's house in Texas. Meanwhile, Leonard catches up with Penny after his summer away, but just as it seems like a relationship is about to start, Leonard must fly to Texas to bring Sheldon home.
The Jiminy Conjecture
Season 3, Episode 2 - Aired September 28, 2009
Leonard and Penny's relationship hits a snag when their first night together is not as special as they expected. Meanwhile, Sheldon and Howard go to great lengths to determine the species of a cricket for a wager they made.
The Wheaton Recurrence
Season 3, Episode 19 - Aired April 12, 2010
When Leonard says "I Love You" to Penny and she doesn't respond in kind, the couple struggle to find a way to keep their relationship alive. Meanwhile, Sheldon has a second encounter with his mortal enemy Wil Wheaton, this time at a bowling alley.
The Recombination Hypothesis
Season 5, Episode 13 - Aired January 19, 2012
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.
The 43 Peculiarity
Season 6, Episode 8 - Aired November 15, 2012
Howard and Raj are intrigued when they notice Sheldon disappears every day at 2:45. When they secretly follow Sheldon down to the basement, they are made even more curious by the number 43 written on a blackboard. Meanwhile, Leonard gets jealous when Penny invites a guy in her history class over to study.
The Hesitation Ramification
Season 7, Episode 12 - Aired January 2, 2014
After Penny's big acting break on NCIS gets cut, Leonard's attempts to help her lead Penny to make a bold relationship move. Meanwhile, Raj tries to improve his "game" before re-entering the dating world, and Sheldon learns how to be funny.
The Gorilla Dissolution
Season 7, Episode 23 - Aired May 8, 2014
A bad day on the set of her movie causes Penny to reconsider the decisions she's made in her career - and her romantic life. Meanwhile, Howard and Bernadette struggle to take care of an injured Mrs. Wolowitz, while Raj gets relationship advice from Sheldon.
The Space Probe Disintegration
Season 8, Episode 12 - Aired January 8, 2015
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 as they go shopping for dresses. The experience highlights the benefits of compromise for Sheldon and Leonard, opening the door for a change in their living situations. Elsewhere, as Raj nervously waits for the results of a space probe he helped to launch, Howard tries to take his mind off it.
The Commitment Determination
Season 8, Episode 24 - Aired May 7, 2015
After Sheldon upsets Amy on their fifth anniversary date night, Sheldon and Amy both think about the state of their relationship. Meanwhile, Sheldon's relationship reflection pushes Leonard and Penny to reexamine their engagement. Raj rethinks his relationship with Emily, while Howard and Bernadette try to make a change to their homelife.
The Matrimonial Momentum
Season 9, Episode 1 - Aired September 21, 2015
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.
The 2003 Approximation
Season 9, Episode 4 - Aired October 12, 2015
When Sheldon learns that Leonard has moved out and is now living with Penny, he reverts to 2003 - a simpler time before he met Leonard and Penny. Howard and Raj form a folk sci-fi band to play live music at Stuart's Comic Book Store.
The Conjugal Conjecture
Season 10, Episode 1 - Aired September 19, 2016
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. When Beverly finds out that her ex-husband might have spent the night with Sheldon's mother, she threatens to leave before the ceremony.
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.
The Stockholm Syndrome
Season 12, Episode 24 - Aired May 16, 2019
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.