Sheldon needs half a billion dollars to prove his latest concept of string theory, which the University cannot afford to fund. Crowdfunding and selling some of his most valuable comic books to Stuart give him a small start. When Raj mentions gambling in Las Vegas, Sheldon goes there but is caught calculating odds by security before he can make any bets. Meanwhile, Amy takes Penny and Bernadette shopping for her wedding dress. She loves an old-fashioned one that the other girls admit that they find ugly, though Penny assures Amy she can make her own decisions about her wedding. Sheldon, however, comes home and sees Amy in the dress and loves how she looks.
Penny, who admits to missing Leonard in "The Roommate Transmogrification", accepts his request to renew their relationship in "The Beta Test Initiation". After Penny suggests having sex in "The Launch Acceleration", Leonard breaks the mood by proposing to her. Penny says "no" but does not break up with him. She stops a proposal a second time in "The Tangible Affection Proof". In the sixth-season episode, "The 43 Peculiarity", Penny finally tells Leonard that she loves him. Although they both feel jealousy when the other receives significant attention from the opposite sex, Penny is secure enough in their relationship to send him off on an exciting four-month expedition without worrying in "The Bon Voyage Reaction". After Leonard returns, their relationship blossoms over the seventh season. In the penultimate episode "The Gorilla Dissolution", Penny admits that they should marry and when Leonard realizes that she is serious, he proposes with a ring that he had been saving for years. Leonard and Penny decide to elope to Las Vegas in the season 8 finale, but beforehand, wanting no secrets, Leonard admits to kissing another woman, Mandy Chow (Melissa Tang) while on an expedition on the North Sea. Despite this, Leonard and Penny finally elope in the season 9 premiere.

After Sheldon has a food truck moved away from the building, Leonard and Penny are shocked to find he is the leader and sole member of the Tenants' Association for the building. Amy doesn't want to be caught in the middle but secretly suggests they rally support from the other tenants to vote Sheldon out. Nobody else supports Leonard so Amy tells them Sheldon was never added to the lease when he moved across the hall with her. Sheldon fires back with his own legal technicality so Amy is forced to support Leonard. She makes Sheldon happy by saying he can be Leonard's official opposition, making Leonard believe he made a mistake. Meanwhile, Howard and Raj find a drone. Raj returns it to the cute owner Cynthia and gets her number. Unfortunately, Cynthia watches footage of Raj on the drone and is immediately turned off.
However, no legal action was required to end production of the other show: as soon as it became known that the show was unlicensed, the actors quit and the producers canceled it.[209] Dmitriy Tankovich (who plays Leonard's counterpart, "Seva") said in an interview, "I'm upset. At first, the actors were told all legal issues were resolved. We didn't know it wasn't the case, so when the creators of The Big Bang Theory started talking about the show, I was embarrassed. I can't understand why our people first do, and then think. I consider this to be the rock bottom of my career. And I don't want to take part in a stolen show".[210]
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