Sheldon's childhood friend from Texas, Tam, is visiting the university with his son. Sheldon does not want to see him and the others wonder why Sheldon has never mentioned Tam. Tam is unaware Sheldon is angry with him, thinking they just naturally drifted apart. Sheldon's brother George does not know the reason either. Sheldon eventually reveals Tam promised he would move to California with Sheldon, but then got a girlfriend and stayed with her, leaving Sheldon feeling abandoned. Tam and Sheldon make up and Sheldon has Leonard take Tam to the airport. Meanwhile, Penny and Bernadette want to get to know Anu, impressed by her connections in the hotel industry. They tell her embarrassing things about Raj and wonder if they can go out with her again after Raj confronts them.
Kunal Nayyar as Rajesh Koothrappali:[46] A particle astrophysicist originally from New Delhi, India. Raj is initially unable to talk to women unless he drinks alcohol. Raj also has very feminine tastes and often takes on a stereotypical female role in his friendship with Howard as well as in the group of four men. Raj later dates Lucy (Kate Micucci), who also suffers from social anxiety, but it eventually ends; he later speaks to Penny without alcohol and thus overcomes his selective mutism. He begins dating Emily and their relationship later becomes exclusive. Raj also has a Yorkshire Terrier named Cinnamon.
In November 2016, it was reported that CBS was in negotiations to create a spin-off of The Big Bang Theory centered on Sheldon as a young boy. The prequel series, described as "a Malcolm in the Middle-esque single-camera family comedy" would be executive-produced by Lorre and Molaro, with Prady expected to be involved in some capacity, and intended to air in the 2017–18 season alongside The Big Bang Theory.[211][212] The initial idea for the series came from Parsons, who passed it along to The Big Bang Theory producers.[213] In early March 2017, Iain Armitage was cast as the younger Sheldon, as well as Zoe Perry as his mother, Mary Cooper. Perry is the real-life daughter of Laurie Metcalf, who portrays Mary Cooper on The Big Bang Theory.[213]
After learning Sheldon went behind their backs to work with the military again, Leonard and Howard say Sheldon is like Thomas Edison, taking credit for others' ideas, while they are more like Nikola Tesla. Leonard and Howard bring in Barry Kripke to help create a better idea than Sheldon's, but Kripke goes to the military himself, cutting all three of them out. Meanwhile, Bernadette fears Ruchi is trying to steal her projects at work while she is on maternity leave and enlists Raj to spy on her. Though he finds proof that Ruchi may be stealing from Bernadette, Raj tries to defend Ruchi like a boyfriend would, pointing out Bernadette's hypocrisy as she would most likely have stolen from other people's projects as well. Ruchi is not happy about this and promptly dumps Raj.

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.
By season seven, Galecki, Parsons, and Cuoco were also receiving 0.25% of the series' back-end money. Before production began on the eighth season, the three plus Helberg and Nayyar, looked to renegotiate new contracts, with Galecki, Parsons, and Cuoco seeking around $1 million per episode, as well as more back-end money.[36] Contracts were signed in the beginning of August 2014, giving the three principal actors an estimated $1 million per episode for three years, with the possibility to extend for a fourth year. The deals also include larger pieces of the show, signing bonuses, production deals, and advances towards the back-end.[37] Helberg and Nayyar were also able to renegotiate their contracts, giving them a per-episode pay in the "mid-six-figure range", up from around $100,000 per episode they each received in years prior. The duo, who were looking to have salary parity with Parsons, Galecki, and Cuoco, signed their contracts after the studio and producers threatened to write the characters out of the series if a deal could not be reached before the start of production on season eight.[38] By season 10, Helberg and Nayyar reached the $1 million per episode parity with Parsons, Galecki, and Cuoco, due to a clause in their deals signed in 2014.[39]

Simon Helberg as Howard Wolowitz:[45] An aerospace engineer who got his Masters at MIT. Howard is Jewish and lived with his mother, Debbie (Carol Ann Susi). Unlike Sheldon, Leonard, Raj, Bernadette and Amy, Howard does not hold a doctorate. He goes into space, training as an astronaut and serving as a payload specialist. Howard initially fancies himself as a womanizer, but he later starts dating Bernadette, and they get engaged and married. Howard also has a tendency to waste money on toys and argues with Bernadette because of his oddly low income as an engineer and her high income as a pharmaceutical biochemist.
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