As one of the most successful and most beloved long-running sitcoms in the history of television, The Big Bang Theory has left an indelible mark on Hollywood, popular culture, and the world at large. The series put a real spotlight on nerd culture, as it chronicled the lives of best friends Sheldon, Leonard, Raj, and Howard and the many other characters who came in and out of their orbit.
Over the course of the series, the show turned out some truly spectacular episodes, some of which easily rank amongst the finest in sitcom history. Here, we're taking a look back at the best episode from each season, and how they all compare.
Season 10: "The Long Distance Dissonance"
The season ten finale isn't really the best episode of the series by any measure, but considering its eventful nature and the overall weak quality of the tenth season, the finale episode "The Long Distance Dissonance" seems like the right choice.
With Amy on the east coast for work at Princeton, Sheldon finds himself once again pursued by past admirer Dr. Ramona Nowitzki. It's only as a result of this that Sheldon realizes what he wants from his future, and he impulsively travels across the country to ask Amy to marry him in a season-ending cliffhanger.
Season 4: "The Justice League Recombination"
The Big Bang Theory explored many of the most fun aspects of nerd culture, and a topic it examined frequently - and even before it was as mainstream as it is today - was the culture of cosplay. In the fourth season episode "The Justice League Recombination," the guys decide to enter the Justice League costume contest being held at Stuart's comic book store and enlist Penny and her dim-witted boyfriend, Zack, to join them and fill out the League.
Not much of major importance goes on in the episode, but it's far and away the best of the season for its emphasis on the group friendship, the inclusion of some hilarious costumes, and Sheldon's Flash-themed daydream sequence.
Season 8: "The Maternal Combustion"
As hard as it may be to believe, considering how prominently both polar opposite characters feature in the series, Sheldon's mother Mary and Leonard's mother Beverly didn't actually meet until the series' eighth season. Although season eight is one of the weaker seasons in the series, this meeting of two totally different minds stands out as one of the season's few highlights.
Another plot in the episode focuses on Stuart's growing overly comfortable stay in the Wolowitz home, which culminates in a hilarious cleaning sequence in which Howard, Raj, and Stuart sing "It's A Hard Knock Life."
Season 11: "The Proton Regeneration"
The love-hate relationship between former enemies, and eventual frenemies, Sheldon Cooper and Wil Wheaton was arguably one of the highlights of the series as a whole. But the eleventh season episode "The Proton Regeneration" took their newly thawed relationship to new, icy levels.
Upon learning that they were seeking a new actor for Professor Proton, Sheldon set out to audition for the role, only to lose out to none other than the nefarious Wheaton himself.
Season 5: "The Hawking Excitation"
The Big Bang Theory amassed plenty of impressive guest stars during its lengthy run, especially from the worlds of both science fiction and science itself. But arguably one of the most impressive recurring roles the series managed to pull off was featuring prominent scientist Stephen Hawking.
In this hilarious episode, Sheldon goes to great lengths to convince Howard to take him to meet his long-time idol, and real hilarity ensues. It also presents the beginning of Sheldon and Hawking's hilarious back and forth relationship.
Season 6: "The Proton Resurgence"
Sometimes, a show lucks into something truly remarkable in the form of a guest star who goes on to become a major part of the series. For The Big Bang Theory, there were many of these, but the most adorable and beloved of them all was Bob Newhart's Professor Proton.
Professor Proton first enters the series once Leonard and Sheldon decide to call upon their childhood hero for a visit. Highlights of the episode include Professor Proton's signature dry banter with Penny, Sheldon's use of his Gino the Neutrino puppet, and Sheldon serenading an ailing Professor Proton with "Soft Kitty."
Season 9: "The 2003 Approximation"
Sheldon Cooper is essentially the poster child for not knowing how to deal with change, and this ninth season episode perfectly depicts that. After newlyweds Penny and Leonard finally move in together on their own, Sheldon essentially reboots himself to his 2003 programming, leading to some both hilarious and touching sequences in which he is forced to face his own anxieties.
But the real highlight of the episode comes in the form of its subplot, which finds best friends Raj and Howard forming their nerd rock band Footprints on the Moon with their Indiana Jones meets Thor song "Thor and Dr. Jones."
Season 12: "The Stockholm Syndrome"
It's rare, and even rarer these days in particular, that a series manages to perfectly stick the landing with its final episode. But The Big Bang Theory managed to do all that and more with its two-part finale, which found Sheldon and Amy winning the Nobel Prize, and the gang making the trek to Stockholm for the awards ceremony.
Many amazing things happen in this finale, offering necessary character development and closure for the series' core characters. But the most important moment of all comes in the form of his acceptance speech, when he finally recognizes and thanks his friends, telling them that he loves them all.
Season 1: "The Pancake Batter Anomaly"
While the series may have been much broader in its early seasons, there's no denying that the first season of the series is one of its strongest, and also one of its most crucial. This episode, one of the last few of the season, introduces a major player in the series: Sheldon's beloved song "Soft Kitty."
Leonard, Howard, and Raj abandon a sick Sheldon in favor of going to a Planet of the Apes marathon. As a result, Penny is left to care for him and learns what a particular young man he is in the process.
Season 3: "The Adhesive Duck Deficiency"
The dynamic between Sheldon and Penny was one of the strongest points of the series on the whole, even if it was sadly underused in the later years. But the third-season episode "The Adhesive Duck Deficiency," in which Penny is now the patient that needs tending to by an exasperated Sheldon, perfectly highlights the success of their odd-couple relationship.
The fact that Penny manages to convince Sheldon to serenade her with "Soft Kitty" alone is a reason to include this episode on this list. It's a real moment of growth for their relationship, and for Sheldon, too.
Season 7: "The Scavenger Vortex"
The Big Bang Theory is often at its best when it focuses on friendships and unusual pairings, rather than leaning too heavily into its mostly contrived central romances. The seventh season adventure episode "The Scavenger Vortex" perfectly highlights that fact.
Featuring the pairings of Sheldon and Penny, Leonard and Bernadette, and Howard and Amy, the episode finds the friends trying to complete a scavenger hunt set up for them by Raj, and hijinks ensue. Clear highlights include Howard and Amy bonding over Neil Diamond singalongs and Raj's adorably elaborate scavenger hunt plans.
Season 2: "The Bath Item Gift Hypothesis"
Genius physicist Dr. Sheldon Cooper learns a lot over the course of the series and grows quite a bit from the young man he is in the series' earliest episodes. But one of the first real lessons and signs of character development he expresses comes about in the second season episode "The Bath Item Gift Hypothesis."
After trying to learn more about and understand the ritual of exchanging gifts for the holidays, Sheldon receives an autographed napkin from Penny that had been signed by Leonard Nimoy. The result? An enthusiastic hug from the hug-averse Sheldon. A Saturnalia miracle indeed.