Sheldon and Amy pick their best-man and maid of honor by experimenting on the gang. Meanwhile, Leonard's self-confidence is still badly damaged after reading his brother's Christmas letter.
Sheldon kicks Amy out of the apartment to work solo, and she and Leonard end up bonding during a series of science experiments; Howard is replaced by Bert in Footprints on the Moon.
Raj meets a girl at the Planetarium, but soon after finds out she is married. Sheldon rents out his old room to use for his work.
When Bernadette won't go into labor, the gang try different tactics to get things started. Also, Wolowitz confronts Bernadette after Amy accidentally reveals she's already chosen their son's name.
Leonard jumps through hoops to help secure the perfect wedding venue for Sheldon and Amy. Also, Bernadette and Wolowitz have a hard time deciding who should stay at home with the kids and who should go back to work.
Leonard, Howard and Raj try to meet Bill Gates, who's meeting with Penny to merge their companies; Sheldon thinks he's the victim of an April Fool's prank.
Leonard runs against Sheldon to be president of the tenants association; Wolowitz and Koothrappali find a drone in the backyard.
Sheldon takes the guys to a cabin in the middle of nowhere to meet a reclusive scientist; Penny and Bernadette improvise Amy's bachelorette party.
Sheldon's comic book store experience changes when writer Neil Gaiman puts Stuart's store on the map; friendships are threatened when Koothrappali takes credit for Penny's astronomical discovery.
Sheldon goes to Vegas to win money for science. Also, Penny and Bernadette take Amy wedding dress shopping, but her terrible choice entangles them in a web of lies.
When Amy's parents and Sheldon's family arrive, everybody is focused to make sure all wedding arrangements go according to plan - everyone except the bride and groom.
The Wolowitzes' life gets complicated when Stuart starts bringing his new girlfriend home. Also, Penny and Leonard talk about starting a family while Koothrappali explores an arranged marriage.
Sheldon won't tell anyone why he's never mentioned Tam, his childhood best friend, so Leonard takes matters into his own hands. Also, Bernadette and Penny take out Raj's fiancée, Anu, for dinner to get the skinny on her.
Amy doesn't have time to work with Sheldon on super asymmetry, so he goes to great lengths to ensure she's available. Koothrappali doesn't want Wolowitz to join him in hosting a show at the planetarium.
When Wolowitz dresses up as Sheldon for Halloween, Sheldon seeks retaliation at Leonard and Penny's Halloween party. Also, Leonard is shocked that Penny doesn't remember their first kiss.
Leonard is caught between a rock and a hard place when he's responsible for distributing extra grant money. Also, Bernadette turns the backyard playhouse into a hideaway from her husband and kids.
Sheldon tries to bond with Amy's father, but when Wolowitz lures Mr. Fowler away with magic tricks, Sheldon has no choice but to bond with Mrs. Fowler. Also, Koothrappali and Anu try to get physical for the first time.
Sheldon and Amy are devastated after learning from a Russian paper that super asymmetry has already been theorized and disproved. Bernadette wants to beat Howard in a popular video game.
A VHS tape from Sheldon's past inspires him and Amy not to give up when they're still feeling down about their theory being disproven. Bernadette turns into a pageant mom when she tries to help Howard with his Magic Castle audition.
