The Big Bang Theory has signed off for good. After 12 years and 277 episodes, fans finally bid farewell to Sheldon, Leonard, Penny and the rest of the hilarious cast in a finale packed with tears and laughter.

Over the years, the popular sitcom has featured plenty of memorable episodes. As we say farewell to the hit comedy -- don't worry, it will live on in syndication -- it's the perfect time to take a look back at the best episodes.

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The Love Car Displacement

Big Bang Theory Love Car Displacement

The 13th episode of Season 4, "The Love Car Displacement," was one of the first episodes to take full advantage of The Big Bang Theory's expanded cast. After Amy (Mayim Bialik) and Bernadette (Melissa Rauch) became full-fledged members of the Big Bang Theory cast, the series changed into an ensemble show about three couples, and "The Love Car Displacement" was a prime example of what the series could now do.

The episode brought all of the characters together in the same story as they road tripped in two separate cars to a science conference. The episode cleverly mixed in the characters' many quirks, the three love stories at the heart of the show as well as the leads' prolific careers in all things science. Different arguments lead everyone to switch hotel rooms, and it all culminates in a hilarious panel featuring the series' seven lead characters. The episode may not feature a big character moment or big plot twist -- it's just the series showing that it can effortlessly weave everyone together in the same story filled with huge laughs.

The Countdown Reflection

"The Countdown Reflection" was the Season 5 finale of The Big Bang Theory and was most notable for featuring the wedding of Howard and Bernadette. The episode takes place in two different times: In the present, Howard is in a space shuttle, awaiting a lift off that will take him to the International Space Station as his friends watch the launch on television. At the same time, flashback segments show the couples' quiet but beautiful wedding ceremony.

This was an episode packed with emotion, as Leonard, Penny, Raj, Sheldon and Amy all served as officiants during the wedding, which took place on top of the apartment building. Why? So that the ceremony could be photographed by the Google Maps satellite. A perfect Big Bang moment. Plus, the palpable worry and love felt by all the characters as they watch Howard's launch, bidding their friend a safe voyage to the stars, was enough to leave us all emotionally fragile as the episode came to a close.

The Love Spell Potential

The Big Bang Theory characters cheer while playing a Dungeons & Dragons game

"The Love Spell Potential," the 23rd episode of Season 6, is quintessential Big Bang Theory. It is a prime example of worlds colliding in the best possible way. While Raj is out on a date with Lucy, Leonard, Sheldon, Howard, Bernadette, Penny and Amy all play a game of Dungeons & Dragons together. The cold open of the episode perfectly highlights the contrast between the male and female groups of the series, as the guys excitedly prep their D&D game while the girls get ready to head out for a weekend in Vegas with the exact same levels of joy.

However, a mishap with airport security sends the girls back home. Then, when all six characters play in the same game, the episode kicks up the hilarity by showing how the girls mix in with something so important to the guys. Add to that Howard's flawless impersonation of actors such as Nicholas Cage and Christopher Walken as the greatest Dungeon Master Sheldon has ever seen and you have the makings of an absolute classic.

The Scavenger Vortex

Big Bang Theory The Scavenger Vortex

Season 7's third episode, "The Scavenger Vortex," easily ranks as one of the funniest of Big Bang Theory's entries -- and not just because it offers us Sheldon holding a bowling ball, exclaiming "my brain is better than everybody's!"

In the episode, Raj puts together a scavenger hunt that takes his friends all across Pasadena. Separated in teams of two, we not only have another classic Sheldon and Penny duo, we are also treated to two duos that rarely team up on the series: Bernadette and Leonard, and Howard and Amy. The race-against-the-clock nature of the episode only adds urgency to the already hilarious hijinks, and Howard and Amy's unexpected bonding over the music of Neil Diamond is a delight. This is an episode that you will find incredibly entertaining, no matter how many times you watch it.

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The Opening Night Excitation

Big Bang Theory Opening Night Excitation

The Season 8 episode "The Opening Night Excitation" just might be the best episode of The Big Bang Theory. Not only does it offer a major character milestone, it is the prime example of everything the series has to offer. Ever since its beginning, the CBS sitcom was about four geeky characters who love comic books and sci-fi movies trying to find love despite their flaws.

In Season 8, Sheldon Cooper, who at one time was the farthest one could be from relationship material, decided to take things with his girlfriend Amy to the next level by finally sleeping with her. For fans of the series, this was a long time coming, and it got the attention and care it deserved. Better yet, Sheldon and Amy's night of passion was juxtaposed with Leonard, Raj and Howard's premiere screening of Star Wars: The Force Awakens -- another thing that was more than a long time coming.

By drawing parallels between the excitement that comes with either a night of intimacy or the long-awaited premiere of a film, "The Opening Night Excitation" is a microcosm of all that The Big Bang Theory is. It's pop culture and relationships. It's fiction and science. Biology, love and spaceships.

The Big Bang Theory stars Jim Parsons, Johnny Galecki, Kaley Cuoco, Mayim Bialik, Kunal Nayyar, Simon Helberg and Melissa Rauch.