When Penny tells Leonard he needs to be more assertive in making decisions for himself, he starts standing up to Sheldon over small things. His confidence makes him want to demand the university support his idea for a plasma physics project. He threatens to quit if the university refuses, alarming both Sheldon and Penny, who consider this to be a risky career move. Sheldon is conflicted on whether or not he is being selfish over Leonard's decision, but Amy suggests that the fact that he is worried over Leonard's motivation proves that he does care about him, which he acknowledges. President Seibert refuses the project, but in order not to lose Leonard, gives him co-leadership over a photon entanglement project, leaving Leonard proud of himself and Penny impressed. Meanwhile, Raj shows Anu his lab, and suggests one possible answer for something he's seen in space might be alien life. When someone mentions this at his observatory presentation, the scientific community starts mocking him as a conspiracy theorist. Raj points out scientists should consider all possibilities when seeking the truth, though this causes people to think he believes in the Loch Ness Monster.
Sheldon is still despondent over the disproving of his and Amy's theory on asymmetry. Leonard brings out a VHS tape of a pep talk that Sheldon recorded as a boy, but it turns out that his father had recorded a long-ago football game over it. Sheldon, however, is buoyed by a halftime pep talk his father gave the team, realizing he and his father had more in common than he previously thought. This causes Amy to view asymmetry and symmetry in another manner and they decide their theory may not be dead after all. Bernadette finds an old tape of Howard preparing to audition for The Magic Castle. She insists he fulfill his dream and audition with her as a coach, drawing on her beauty pageant experience. Howard eventually decides to audition his own way, and promptly botches his chances by accidentally destroying a judge's Rolex.

Leonard's mother Beverly visits, and he is thrilled when she takes an interest in his work. However, when he learns that she is doing research on him for a new parenting book, he is furious. He prepares to tell her how she let him down over the years, but instead chooses to accept and forgive her, and forgive himself for holding onto that resentment for so long. Beverley is touched that he forgave her and they share a genuine hug. Meanwhile, Anu gets a job offer in London. Raj prepares to fly out and propose to her, ready to follow her if she accepts. Howard stops Raj at the airport, saying there is a better match out there for him, convincing Raj to return home. Stuart and Denise are bothered by her creepy roommate Mitch, while Bernadette and Howard are tired of Denise constantly staying overnight with Stuart at their house. Stuart says he is ready to move in with Denise, and they say they love each other while convincing Mitch to move out.
Warner Bros. Television controls the online rights for the show.[159][160] Full episodes are available at tv.com, while short clips and recently aired full episodes are available on cbs.com.[161] In Canada, recent episode(s) and pictures are available on CTV.ca.[162] Additionally in Canada, the first six seasons are available for streaming on Bell Media's CraveTV.[163] After the show has aired in New Zealand the shows are available in full online at TVNZ's on demand web service.
Leonard and Sheldon are brilliant physicists—geniuses in the laboratory but socially challenged everywhere else. Enter beautiful, street-smart neighbor Penny, who aims to teach them a thing or two about life. Despite their on-again, off-again relationship in the past, Leonard and Penny have finally gotten married. Even Sheldon has found a female companion, entering into a "relationship agreement" with neurobiologist Amy Farrah Fowler, and he recently took their relationship to the next level by marrying her after a long courtship. In their free time, Leonard and Sheldon enjoy fantasy role-playing games with their ever-expanding universe of friends, including fellow scientists Koothrappali, Wolowitz, and Wolowitz’s adorable microbiologist wife, Bernadette, who is adjusting to life with their two children.
Sara Gilbert as Leslie Winkle (recurring season 1, starring season 2, guest seasons 3, 9):[47][48][49] A physicist who works in the same lab as Leonard. In appearance, she is essentially Leonard's female counterpart and has conflicting scientific theories with Sheldon. Leslie has casual sex with Leonard and later Howard. Gilbert was promoted to a main cast member during the second season but resumed guest star status because producers could not come up with enough material for the character.[47] Gilbert returned to The Big Bang Theory for its 200th episode.[50]
The Big Bang Theory is an American television sitcom created by Chuck Lorre and Bill Prady, both of whom served as executive producers on the series, along with Steven Molaro. All three also served as head writers. The show premiered on CBS on September 24, 2007 and concluded on May 16, 2019, having broadcast a total of 279 episodes over 12 seasons.[3]
Star Trek in particular is frequently referenced and Sheldon identifies strongly with the character of Spock, so much so that when he is given a used napkin signed by Leonard Nimoy as a Christmas gift from Penny he is overwhelmed with excitement and gratitude ("I possess the DNA of Leonard Nimoy?!").[73] Star Trek: The Original Series cast member George Takei has made a cameo, and Leonard Nimoy made a cameo as the voice of Sheldon's vintage Mr. Spock action figure (both cameos were in dream sequences). Star Trek: The Next Generation cast members Brent Spiner and LeVar Burton have had cameos as themselves,[74][75] while Wil Wheaton has a recurring role as a fictionalized version of himself. Leonard and Sheldon have had conversations in the Klingon language.

When Leonard receives a braggy Christmas letter from his brother, he feels bad about how little he and Penny have achieved in the past year. Leonard wonders if he and Penny should be thinking about the next step after two years of marriage, like buying a house or having a baby. Penny tells him she wants to do all those things someday, but she has a bunch of stuff she would like to do first.

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