Leonard and Penny 's relationship has been a major subject in the series since the beginning of season one pilot episode. Most of the season finales involve Leonard's relationship with Penny in some way. She asked favors of him and talked and visited him nearly every day. When no one else showed up she suspected their evening was supposed to be a date. At the end of the season 1 after another bad break-up, she confessed she wanted to go out with a guy like him and with that, Leonard asked her out which she accepted.
Their date went well though Penny wanted to take it slow. Afterwards, Penny gets the idea that he won't date a girl that doesn't have a college degree derailing a second date at that time.
First Relationship Leonard and Penny's relationship had many awkward moments. At the end of Season 2 , the episode " The Monopolar Expedition ", Leonard and the others were arranged to go to the North Pole for three months.
In that episode, she gave him a blanket with sleeves and gave him a long hug, which made Leonard concerned about leaving her. When he asked her what it meant, she said it was just a going away present. After he left and she closed the door, she whispered, "It means I wish you weren't going" revealing her hidden feelings.
Leonard gave her a preserved snowflake which she loved and they began going out again. After a quick trip to Texas to bring Sheldon home, the new couple finally consummated their relationship which they both described as weird. After realizing how weird the relationship was, they decide to return to being friends, but quickly resumed their romance within a few seconds.
Throughout season 3, they learned about each other and explored the limits of their relationship. There were some fights like Leonard belittling her for believing in psychics " The Psychic Vortex " or Penny not telling him about her letting an ex-boyfriend stay in her apartment " The Guitarist Amplification ", though there was a lot of make-up sex and a lot of compromises mainly by Leonard.
Sheldon was often frustrated with the constant presence of Penny within his inner circle and the couple many times were treating him like they were his parents.
Wil Wheaton told Penny that it would be kinder to break-up with Leonard right away, which later was revealed to be a trick to win the bet, but Penny had already broken up with Leonard, believing it would help him. Ironically it was Sheldon who was responsible for keeping them together as friends.
Watching him sleep after they put him to bed, they decided that they could move on as friends. In the season 3 finale " The Lunar Excitation ", Penny started dating Zack and later reprimands Leonard for ruining him and destroying her ability to tolerate idiots and takes Leonard so they have sex.
In Season 4 , Leonard and Penny's relationship had a bit of awkwardness. In " The Love Car Displacement ", Leonard and Penny have a one-night stand and Leonard thinks they've gotten back together, but Penny says it was a one-time thing and Leonard gets upset and results in him driving fast and being followed by the police.
Leonard's next girlfriend Priya Koothrappali wanted Leonard to stop hanging out with Penny. Penny agreed to it to help Leonard move on with his relationship.
Penny hated Priya because of that and got upset with not talking to Leonard as much. At the end of Season 4, in " The Roommate Transmogrification " she admitted to Raj she regretted breaking up with Leonard, and ends up 'sleeping' with Raj. Although it was revealed later in " The Skank Reflex Analysis " that they didn't actually have sex, but they briefly hooked up.
Second relationship Leonard and Penny 2. In his fantasy, things did not go well the second time around, but he decided to go ahead and ask her out anyway, and Penny agreed to go as long as he was sure. She also has issues since other members of her family were pregnant when they got married. Leonard and Penny's fantasies regarding their possible reconciliation proved to have their merits when in the following episode, , Season 5 Episode 14 , " The Beta Test Initiation ", it was shown that the two were contemplating to be official again.
However, to avoid the mistakes from their first time together, they decided to take things slow by treating the relationship as a beta test , and even went to the length of presenting each other Bug reports to settle any issues. Things seemed to be going well by the end of the episode, with Penny kissing Leonard at his doorstep after their date and at the shooting range. In " The Friendship Contraction ", it was apparent that the two are definitely in a relationship again, though they taking things slow this time around, and the beta test that was still very much going on.
During a blackout at the apartment , Leonard opted to hang out with Penny at her apartment and the two were about to make out when Sheldon interrupted them. In " The Launch Acceleration ", Penny suggested that they move up their relationship and get intimate ; however Leonard ruined the mood when he asked her to marry him while they were having sex making their relationship feel weird to Penny.
Season 6 starts with them on a date in " The Date Night Variable " where a lonely Raj crashes their date and insists that Penny tell Leonard that she loves him. Leonard wants to talk about their relationship; however she has had a hard day and wants to just hang out together. Penny is expressing doubts about her feelings for Leonard, though she claims to be happy with the relationship in " The Decoupling Fluctuation ". A little fight after Leonard asked Penny to marry him while they were having sex.
She almost tells Leonard about her doubts and then ends up sleeping with him after looking into his sad eyes. Later when Sheldon and Alex enter the apartment, Penny tells her about Leonard and their five year experiment together relationship and then she leads him off to her apartment for sex.
In the Halloween theme episode " The Holographic Excitation ", Penny gets advice from Bernadette that you get out of a relationship what you put into it and that maybe Penny should get more interested in Leonard's work it is also revealed that, up until this point, Penny's view of their relationship had been one-sided in her favor.
She visits his lab and is wowed by his holographic images and says that she sometimes forgets how smart he is. Penny heats up their relationship by starting to engage in sex in different locations, twice in his lab and twice in the TARDIS photo booth at the Halloween party. Penny and Leonard, Valentine's Day Leonard tells Penny to ask him to marry her when she is ready.
In the episode " The 43 Peculiarity ", Penny is working on a class oral project with an English student, Cole , who makes Leonard jealous.
Leonard follows Cole down the stairs warning him about Penny's boyfriend, the " gang leader". Penny witnesses his deception and gets mad at Leonard telling him that he has nothing to worry about because she chooses to be with him and that he knows that she loves him.
This pronouncement shocks both of them since Penny has never told Leonard that she loves him and she runs off scared before she breaks into tears. At the same time, Sheldon's assistant Alex Jensen is starting to hit on Leonard though he doesn't recognize her intentions. In " The Egg Salad Equivalency ", Alex asks Leonard out to dinner after he expresses an interest in the Physics lecture she is going to and this attention really startles Leonard. He also didn't tell Penny about Alex's actions which made her feel really insecure about their relationship.
Leonard apologizes by showing up at her door playing a little ditty on his cello. He asks her if she's all right with it, but she only agrees not to hurt his feelings and even tells Sheldon. She does try to get him admit that Sheldon can't get along without him. Amy plans to move in with Sheldon as roommates. When Amy confronts Penny since she can't move in with Sheldon, Leonard overhears the conversation. Penny tells him that he never asked her if she was ready. Amy also scares Penny when in anger says that she and Penny should move in together.
Penny feels that all the efforts never meet the expectations and she will end up disappointed. At dinner, Penny sees an old boyfriend proposing to the girl that broke them up. Leonard again tries to propose and Penny stops him. They begin to argue in front of Howard and Bernadette who have their own issues that night. Penny finally admits that she has commitment issues. Leonard then puts the responsibility of proposing on her and that she should do it when she's ready.
In the end, she does ask him to be her valentine. Her dreams had always been to become a famous movie star and live a glamorous life. Anything less than that she felt was settling. Her epiphany came to her that she is passionate about her boyfriend Leonard and all her wonderful friends. Penny will miss him, but knows that it is a good opportunity and sends him off. At the airport , she is fussing over him like a wife sending her husband off on a business trip. She also has to watch Sheldon over the summer, too.
Goodbye for four months. In " The Hofstadter Insufficiency ", Leonard hurts Penny because he seems to be having such a great time on the ship; she thinks that he is not even missing her. In " The Deception Verification ", Leonard makes up for it by showing up early and hides in her apartment so that they can spend time together a couple before telling the gang that he's back.
It works until Amy and Sheldon find them together after they think that Penny is cheating on Leonard. In " The Raiders Minimization ", Penny purchases a psychology book that Beverly Hofstadter has written about all his problems growing up for a night school class. Leonard finds out that Penny will do things he wants to do [ditch going to a sports bar, watch geeky shows, and have sex] and uses her. Leonard mentions it to Howard, who fails to try it with Bernadette, so his actions make it back to Penny.
She dresses up for sex tempting him and then for revenge makes him Skype with his mother to discuss his actions much to Leonard's disgust. Leonard mentions that Penny never does anything like that, except for sex which doesn't count. Penny is determined to romance Leonard.
Raj can only suggest that she cook for him or reenact a scene from a romantic movie. Finally after a candlelight dinner, Penny puts on some romantic music, spreads rose petals into her neatly cleaned bedroom and presents Leonard with a first edition of his favorite book from when he was growing up, The Hitchhiker Guide to the Galaxy.
Unfortunately, Leonard had already purchased the book after they had seen it in a used bookstore together. Penny gets upset telling him about all the thoughtful things he had done for her and shows him her collection. An airplane ticket, a rose given to her "just because" and the eleven page letter he wrote her after the first time they slept together.
Leonard was very touched that she kept all these things. Penny planning a crap storm of romance for Leonard. In " The Thanksgiving Decoupling ", Penny reminisces about a Thanksgiving she had in Las Vegas with former boyfriend Zack Johnson which included one of those "silly fake weddings". Penny appears devastated when her friends inform her that the wedding was real and she is Mrs. Penny and Leonard argue about how quickly she should get her annulment so Penny invites Zack over to their Thanksgiving dinner at Howard's mother.
Zack appears as dimwitted as ever telling them that breaking up can be hard on the kids which they don't have. Tensions between Penny and Leonard rise even more when Leonard sarcastically says marrying Zack was "a good call", which leads to Penny calling him out for throwing her mistakes in her face and being a jerk about this situation. Finally, Penny and Leonard make up and she tells him that the next time she gets married it will be for real, for love jokingly or for money.