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.

The episode was rated 7.53 from 3427 votes.

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.

The episode was rated 7.54 from 3563 votes.

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.

The episode was rated 7.55 from 3843 votes.

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.

The episode was rated 7.56 from 4205 votes.

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.

The episode was rated 7.57 from 3509 votes.

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.

The episode was rated 7.57 from 3639 votes.

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."

The episode was rated 7.60 from 3264 votes.

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.

The episode was rated 7.61 from 3591 votes.

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.

The episode was rated 7.65 from 3265 votes.

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.

The episode was rated 7.65 from 3074 votes.

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.

The episode was rated 7.68 from 3540 votes.

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 episode was rated 7.68 from 4028 votes.

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.

The episode was rated 7.80 from 3906 votes.

In the episode "The Change Constant" of The Big Bang Theory, Sheldon and Amy are eagerly awaiting some big news. It was a powerful episode that made many viewers think about life and how much it can change over time. One viewer commented that the scene between Sheldon and Penny at the bar was especially thought provoking and really made her reflect on her own life.

The ending of the episode was especially powerful. From Sheldon's reaction to Penny's comforting words and the scene with the elevator, viewers were moved. One viewer commented that this was the best episode of the entire show and that they are hoping the season finale will be as good.

The episode was rated 8.32 from 3277 votes.

The Big Bang Theory's series finale, The Stockholm Syndrome, was a powerful and emotional episode that encapsulated the show's 12-season journey perfectly. The gang traveled together for one last time, as Bernadette and Wolowitz left their kids for the first time, Penny and Leonard tried to keep a secret, Sheldon and Amy stuck together, and Koothrappali made a new friend. Despite the fact that there were no guest stars, the episode still managed to tug at heartstrings and leave viewers with a sense of closure.

This finale was a true testament to the show's longevity and impact. After 12 amazing seasons, The Big Bang Theory still managed to surprise us with a genuinely funny and heartwarming episode. From Sheldon's Nobel Prize speech to the show's surprise Buffy the Vampire Slayer reference, the finale truly put a lot of heart into the series. Fans were truly moved by this episode, and with the show coming to an end, they will miss these characters and the laughter they provided.

The episode was rated 8.54 from 2611 votes.