Penny worries that she has ruined her relationship with her friends; Sheldon takes over the paintball team.
Amy is caught in the middle when Penny and Sheldon get into an argument over a pre-owned chair; Leonard tries to make his long-distance relationship more exciting.
Amy and Leonard try to become better acquainted; Bernadette, Howard and Mrs. Wolowitz spend the weekend together.
Raj wants a girlfriend, so Penny introduces him to a woman he can communicate with.
Wil Wheaton invites Leonard and Sheldon to a party at his house; Howard receives an opportunity.
Sheldon finds himself competing with the gang for his mother's (Laurie Metcalf) attention when she visits.
An attractive comic book artist tests Leonard and Priya's relationship; Sheldon tries to scare his friends.
Amy is devastated when Penny and Bernadette shop for wedding dresses without her.
Leonard and Penny spend time alone; Sheldon tries to face his fear of birds.
Sheldon is jealous when Stuart (Kevin Sussman), a guy from the comic book store, asks Amy out on a date.
Leonard must face the bully who targeted him in high school; Penny confronts her past actions.
Amy is upset with Sheldon when he isn't impressed with her recent accomplishment; Howard struggles with Bernadette's aversion to children.
Everything could change when Leonard spontaneously invites Penny to a romantic dinner.
Penny and Leonard experiment with their new relationship; Raj forms a bond with his phone's virtual assistant.
Leonard starts to reconsider his friendship with Sheldon; Wolowitz tries to choose his astronaut nickname.
Sheldon goes to work with Amy in her lab when the university forces him to take a vacation; Bernadette asks Howard to sign a pre-nup.
Sheldon and his nemesis, Kripke (John Ross Bowie), compete for a corner office; Penny feels uncomfortable after receiving a gift from Amy.
Sheldon's routine is turned upside down when his barber gets sick; Wolowitz questions his decision to go into space.
Sheldon plans a video game marathon with the guys instead of attending a birthday party for Amy's aunt.
When Penny buys Leonard and Sheldon "Star Trek" collectibles, Sheldon finds himself haunted by Mr. Spock; after a blind date, Raj believes he has met his future wife.
When Wolowitz works with Stephen Hawking, Sheldon is determined to meet the famous scientist.
Knowledge of Howard's sexual history makes Bernadette reconsider their future together.
Wedding plans are jeopardized when NASA reschedules Howard's mission; Leonard says something in the bedroom that surprises Penny.