Bernadette receives her PhD and the gang begin to tease Wolowitz for being the only one among them who isn't a doctor. Meanwhile, Koothrappali becomes Sheldon's new flatmate after hearing Leonard and Priya engaging in a `Star Trek' bedroom fantasy.
Raj attempts to cure his anxiety about talking to women, while Penny uses Bernadette to spy on Leonard and his girlfriend.
Sheldon agrees to take part in a short lecture series at the university, but worries that the students don't seem to like him. On Amy's advice, he asks Penny to give him acting lessons so that he can engage with his audience better.
Tensions run high when Bernadette runs into her hulk of an ex-boyfriend at a science conference. Threatened by Bernadette's ex-boyfriend, Wolowitz has an argument with Bernadette and causes chaos.
Sheldon and Amy experiment on their friends by spreading gossip, while Howard takes a big step in his relationship with Bernadette.