The Thespian Catalyst (2011)

Sheldon guest lectures at the university, but his teaching style is unfunny, boring, dismissive, and altogether intolerable, leading to numerous blogs and Tweets about how awful he is – something that amuses the rest of the gang but devastates Sheldon. Amy tells Sheldon that he needs to improve his communications skills, and recommends he take acting lessons. He convinces Penny to give him acting lessons and behaves in a stubborn and condescending manner, eventually driving Penny to start drinking wine straight out of the bottle. Later, when they try to study an actual play, Sheldon insists that they study a play that he wrote, which is based upon a Star Trek fan-fiction he wrote involving Spock coming to his childhood home to take a younger Sheldon to the 23rd century and work on the Starship Enterprise. A few minutes into the play, Penny, who is playing Spock while Sheldon plays his own mother, prompts him to be sad to see Sheldon leave with Spock. To her surprise, it is revealed that subconsciously, Sheldon misses his mother despite all their disputes concerning religion. Penny quickly realizes what's going on and calls his mother, telling her she "broke her son".

Meanwhile, Raj develops a crush on Bernadette after she calls him a "hottie" and starts fantasizing about her. After two daydreams in which a departing Howard tells Raj to take care of Bernadette sexually, he decides that he's "definitely not gay". In Raj's last daydream, he and Bernadette perform a Bollywood style dance number, and he says that, dance number aside, he's still very much not gay.

Title reference: Sheldon getting Penny to give him acting lessons so he can become a better teacher.