The Big Bang Theory

Sheldon and Amy's honeymoon runs aground in New York, while Penny and Leonard discover they are uncomfortably similar to Amy's parents. Raj insults physicist Neil deGrasse Tyson and starts a twitter war.

Sheldon and Amy drive themselves crazy trying to figure out what "perfect gift" Leonard and Penny gave them for their wedding. Raj decides he wants to settle down and asks his father to arrange a marriage for him.

Howard's life gets complicated when Stuart starts bringing his new girlfriend home. Penny and Leonard talk about starting a family while Raj 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. Bernadette and Penny take out Raj's fiance, Anu, for dinner to get the skinny on her.

Amy doesn't have time to work on a project, so Sheldon goes to great lengths to ensure she can work with him even if it means sabotaging her career in the process. Raj doesn't want Howard to join him in hosting a show at the planetarium.

When Howard dresses up as Sheldon for Halloween, Sheldon seeks retaliation at Leonard and Penny's Halloween Party. 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. Bernadette turns the backyard playhouse into a hideaway from her husband and kids.

Sheldon tries to bond with Amy's father, but when Howard lures Mr. Fowler away with magic tricks, Sheldon has no choice but to bond with Mrs. Fowler. Raj and Anu try to get physical for the first time.

Sheldon and Amy are devastated learning from a Russian paper that Super Asymmetry has been discovered and disproven. Ultra-competitive Bernadette asks Stuart's girlfriend, Denise, to teach her how to beat Howard in a popular videogame.

Sheldon and Amy are still down about their theory being disproven, but a VHS tape from Sheldon's past inspires him not to give up. Bernadette turns into a pageant mom when she tries to help Howard ace his Magic Castle audition.

Penny and Leonard organize a paintball game that results in mayhem when Sheldon is jealous of Amy. Raj catches Anu with her ex-boyfriend, and Stuart doesn't want to move in with Denise.

Penny's ex-boyfriend, Zack, and his wife want a baby, but when Zack is infertile, they ask Leonard to help. Raj attempts to mend things with his ex-fiancée, Anu.

Sheldon and Amy's super asymmetry theory is proven by two physicists, Dr. Pemberton and Dr. Campbell from Chicago, who then try to kick Amy off the Nobel nomination. Bernadette has a big success at work, and Penny's going to be a part of it.

Sheldon is thrilled to help Bernadette and Howard 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 seduce an abstaining Leonard to ruin his "donation" for her ex-boyfriend, Zack, and his wife, Marissa. Howard, Bernadette, Anu and Raj turn Raj's canceled bachelor party into a couple's trip aboard the "vomit comet."

The gang finds out Wil Wheaton hosts a celebrity Dungeons and Dragons game involving William Shatner, Joe Manganiello, Kareem Abdul-Jabbar and Kevin Smith. Deception and betrayal are the path to make it to the one open seat.

Penny and Bernadette go to San Diego for a pharmaceutical sales convention, leaving Howard in charge of the kids. Sheldon finds a book on experimenting on kids, and the guys plus Amy make a day of it.

Pemberton and Campbell charm America on a publicity tour, so Sheldon and Amy bring Nobel laureates Kip Thorne, George Smoot and Frances Arnold to their side. Halley's fear of the dark leads to conflict for Howard, Bernadette and Stuart.

Amy has a meltdown due to the pressure associated with winning a Nobel Prize. Raj and Howard try to relive the good old days after Howard buys a scooter that looks like the one he had years ago.

Raj 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, and Sheldon and Amy aren't sure whether they should turn him in or not. Howard is surprised to learn that Bernie 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.

Everything changes as Sheldon and Amy await big news.

Bernadette and Howard leave their kids for the first time; Penny and Leonard try to keep a secret; Sheldon and Amy stick together; and Raj makes a new friend, as the gang travels together into an uncharted future.

Johnny Galecki and Kaley Cuoco will lead fans on a trip down memory lane, sharing some of the best-kept backstage secrets and personal memories from the past 12 years.