The Big Bang Theory — Season 12

During this 30-minute special retrospective, series stars Johnny Galecki and Kaley Cuoco take viewers behind the scenes of the longest-running multi-camera comedy series in television history.In the special, Galecki and 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. They will reveal their favorite moments playing beloved characters Leonard and Penny, and revisit some of the most memorable stories from "The Big Bang Theory Stage." In addition, the special will feature a tour of the iconic sets, including Leonard and Sheldon's apartment.

Fans of much-loved sitcom The Big Bang Theory, including Sofie Hagen, Joe Swash and Jamie Laing, discuss the biggest, funniest and nerdiest moments from the show and reveal their favourite clips

Sheldon and Amy's honeymoon runs aground in New York, while Penny and Leonard discover they are uncomfortably similar to Amy's parents, Mr. and Mrs. Fowler. Also, Koothrappali 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. Also, Koothrappali decides he wants to settle down and asks his father to arrange a marriage for him.

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.

When Sheldon won't tell anyone why he's never mentioned Tam, his childhood best friend, 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.

When Amy doesn't have time to work on super-asymmetry, Sheldon goes to great lengths to ensure she's available to work with him even it if means accidentally sabotaging her career in the process. Also, 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 discovered and disproven. Also, 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. Also, Bernadette turns into a pageant mom when she tries to help Wolowitz ace his Magic Castle audition.

Penny and Leonard organize a paintball game that results in mayhem when Sheldon is jealous of Amy. Also, Koothrappali 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 for help. Also, Koothrappali attempts to mend things with his ex-fiancée, Anu.

When Sheldon and Amy's super asymmetry theory is proven by two physicists, Dr. Pemberton and Dr. Campbell from Chicago, they're thrilled, until they try to kick Amy off the Nobel nomination. Also, Bernadette has a big success at work and Penny's going to be a part of it – whether she wants to or not.

Sheldon is thrilled to help Bernadette and Wolowitz navigate bureaucratic paperwork, until he discovers they are breaking the law. Also, 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. Also, Wolowitz, Bernadette, Anu and Koothrappali turn Koothrappali's canceled bachelor party into a couple's trip aboard the "vomit comet".

When 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.

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

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

The concept of what it would mean for women everywhere if Amy were to win a Nobel Prize causes Amy to have a meltdown. Also, 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. Also, 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. Also, Wolowitz is happily surprised to learn that Bernadette wasn't the only waitress at the Cheesecake Factory who had a crush on him back in the day.

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. Also, 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; and Koothrappali makes a new friend, as the gang travels together into an uncharted future.