Wolowitz questions his engineering abilities when he and Sheldon can’t get a toy drone to fly. Meanwhile, a cancelled flight nearly prevents Leonard from giving the commencement address at his…

Penny buys Leonard and Sheldon “Star Trek” collectibles as a thank-you, leading Sheldon to be haunted by Mr. Spock. Meanwhile, Raj decides he has met the “Future Mrs. Koothrappali” after…

Penny plays Matchmaker for Raj, which results in him finding a girl he is comfortable talking to.

A fight between Sheldon and Penny leaves Amy caught in the middle, while Leonard tries to spice up his long-distance relationship with Priya.

When Bernadette receives her PhD, Wolowitz feels emasculated. Raj and Leonard swap places and Penny does something she’s regrets.

Sheldon and Amy decide to start several rumors about the others as a test. Meanwhile, Howard takes his relationship with Bernadette to even higher level.

A squabble between Leonard and Penny sees Sheldon playing mediator, though out of his own incovenience from the sitiation rather than altruism.

The guys’ plan to work over the summer at the North Pole makes Penny revaluate her feelings for Leonard.

Raj gets an inflated ego and makes a play for Penny after being referenced in a magazine article.

Raj’s parents set him up on a blind date, but just when he discovers he can talk to her, she shows interest in Sheldon.