Sheldon and Amy's honeymoon runs aground in New York; Penny and Leonard discover they are uncomfortably similar to Amy's parents; Koothrappali insults physicist Neil deGrasse Tyson and starts a Twitter war.
Sheldon and Amy go crazy trying to figure out what "perfect gift" Leonard and Penny gave them for their wedding; Koothrappali decides to settle down and asks his father to arrange a marriage for him.
Life gets complicated when Stuart starts bringing his new girlfriend home; Penny and Leonard talk about starting a family; Koothrappali explores an arranged marriage.
When Sheldon won't tell anyone why he's never mentioned Tam, his childhood best friend, Leonard takes matters into his own hands; Bernadette and Penny take Raj's fiancee out to dinner to get to know her.
When Amy doesn't have time to work on super-asymmetry, Sheldon 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; Leonard is shocked when Penny doesn't remember their first kiss.
Leonard is caught between a rock and a hard place when he becomes responsible for distributing extra grant money; Bernadette turns the backyard playhouse into a hideaway to get away 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; 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 discovered and disproved; Bernadette wants to beat Howard in a popular video game.
A VHS tape from Sheldon's past inspires him not to give up; Bernadette turns into a pageant mom when she tries to help Wolowitz with his Magic Castle audition.
Penny and Leonard organize a paintball game, which results in mayhem when Sheldon becomes jealous of Amy; Koothrappali catches Anu with her ex-boyfriend; Stuart doesn't want to move in with Denise.
Penny's ex-boyfriend Zack learns that he is infertile, so he asks Leonard for help; Koothrappali attempts to mend things with his ex-fiancee Anu.
Sheldon and Amy are thrilled when their super asymmetry theory is proven by two physicists, until they try to kick Amy off the Nobel nomination; Bernadette has a big success at work.
Sheldon is thrilled to help Bernadette and Wolowitz navigate bureaucratic paperwork, until he discovers they are breaking the law; Leonard is disappointed when his friends exclude him from a scientific project.
Penny tries to throw a wrench into Leonard's plan to be a sperm donor for her ex-boyfriend; Wolowitz, Bernadette, Anu and Koothrappali turn Koothrappali's canceled bachelor party into a couple's trip aboard the "vomit comet."
The gang uses deception and betrayal to make it to the one open seat at Wil Wheaton's celebrity Dungeons and Dragons game with William Shatner, Joe Manganiello, Kareem Abdul-Jabbar and Kevin Smith.
When Penny and Bernadette go to San Diego for a pharmaceutical sales convention, Wolowitz is left in charge of the kids; Sheldon finds a book about experimenting on kids.
When competitors Pemberton and Campbell charm America on a publicity tour, Sheldon and Amy try to win over Nobel laureates Kip Thorne, George Smoot and Frances Arnold; Halley's fear of the dark leads to opportunity and conflict.
The weight of winning a Nobel Prize weighs heavy on Amy's shoulders; Koothrappali and Wolowitz try to relive the good old days after Wolowitz buys a scooter that looks like the one he had years ago.
Koothrappali is worried people won't take him seriously in his own field after publishing a paper that suggests he may have discovered alien life; Leonard wants to be the principal investigator on a plasma physics study.
Kripke has proof that Dr. Pemberton plagiarized his thesis in college, and Sheldon and Amy aren't sure if they should turn him in or not; Wolowitz learns that Bernadette wasn't the only waitress at the Cheesecake Factory who had a crush on him.
Leonard is pleasantly surprised when Beverly comes to visit and she's genuinely kind to him, until he finds out the real reason she's there; Denise and Stuart overstay their welcome at the Wolowitz house.
Sheldon and Amy await big news.
Bernadette and Wolowitz leave their kids for the first time; Penny and Leonard try to keep a secret; Sheldon and Amy stick together; Koothrappali makes a new friend; the gang travels together into an uncharted future.