The whole universe was in a hot, dense state and 12 years later The Big Bang Theory finally came to an end. After more than a decade of nerdy television, the CBS comedy finally decided to call it quits once it had accomplished everything it had set out to do, and more.
Despite most shows failing to deliver on their final seasons and leaving audiences displeased or torn in one way or another, The Big Bang Theory closed out their historic run with the highest ratings it had had in years, including having two episodes rated 9 or better on IMDb for only the second time in the entire series.
The Grant Allocation Derivation, Episode 7 (7.4)
One of the perks of being the president of the university is that you can pass menial tasks down to people below you - that's exactly what happened during this episode when President Siebert instructs Leonard to distribute grant money to somebody in the science department (so that Siebert doesn't look like the bad guy when he picks one person and leaves everyone else out).
Everyone in the department begins to try and bribe Leonard into giving them the grant money (including his friends) and a pressured Leonard finally decides to spite all of the leeches and gives the grant money to himself for his own research. Power move, Leonard - respect.
The Consummation Deviation, Episode 8 (7.4)
It was rare for Sheldon to truly bond with anybody, but since he married Amy at the end of season 11 he decided that he should get to know her family better. In that light, Sheldon plans a fun-filled day with Amy's dad, but the day turns into a dud as neither of the men has anything in common.
Things only get worse when Amy's dad starts to bond with Howard over magic, leaving Sheldon to try and hang out with Amy's mom instead. During their conversation, Amy's mom reveals that she doesn't like Sheldon because he keeps Amy from her... which isn't true and it's revealed that Amy uses Sheldon as an excuse to get out of spending time with her mother. Yikes.
The VCR Illumination, Episode 10 (7.5)
Season 11 ended on the cliffhanger that Amy and Sheldon had made a groundbreaking scientific discovery and much of the last season revolved around them proving their theory. However, they both get discouraged during this episode when their theory is proven false and they realize they did all of that work for nothing.
Luckily, Sheldon gets inspired by a videotape from his younger self (played by the boy from Young Sheldon) and also by a speech from his father that appears on the tape - which leads Sheldon and Amy to realize their paper might not be disproved after all.
The Donation Oscillation, Episode 15 (7.5)
While she had implied it several times throughout the series, it was a little heartbreaking for Leonard when Penny revealed that she never wanted to have kids. So, when Penny's ex-boyfriend Zack shows up and asks Leonard to be his sperm-donor in order to make a child with his wife, Leonard decides to agree so that he can technically have a biological child.
Unfortunately, Penny isn't thrilled about the subject and tries to sabotage Leonard from going through with it, only for Leonard to decide that he doesn't want to make a child of his own that he couldn't raise.
The Wedding Gift Wormhole, Episode 2 (7.7)
It takes quite a bit of scheming to outsmart two of the brightest genius' on the planet, but Leonard and Penny managed to pull it off when they gave Sheldon and Amy an ambiguous wedding gift with no explanation of what it was for or how it worked. Sheldon and Amy spend the episode trying to decipher its purpose, only to concoct completely made-up scenarios in their head of what they think it's for which eventually leads them on a scavenger hunt to a coffee shop.
At the coffee shop, they think they find several thoughtful gifts and thank Penny and Leonard for how meaningful their present was... to which Leonard and Penny have no idea what they're talking about.
The D&D Vortex, Episode 16 (8.0)
The guys had played several games of D&D throughout the seasons, but when they found out that Wil Wheaton was part of a celebrity D&D night and that the group had an open slot, the group begins to do anything they possibly can to get themselves into the game.
Eventually, they all end up coming on too strong and freaking all of the celebrities out to the point where they get themselves kicked out. At the end of the episode, the guys are back in their apartment playing D&D just the four of them - and they get a picture from Wil of all the girls playing D&D with the celebs.
The Maternal Conclusion, Episode 22 (8.0)
Nobody gets to choose their parents and it's a complete luck-of-the-draw situation, but Leonard really didn't luck out with his mother. The woman who used her children as science experiments (Leonard the most) showed up for her last appearance on the series and it seemed as though she was actually getting along and bonding with Leonard... until it's revealed that she's just doing it for more research.
Leonard finally breaks down and is about to tell her how he truly feels about her - but stops and realizes he has to accept his mother for who she is if she's ever going to accept him for who he is. The mother and son forgive each other and then embrace.
The Imitation Perturbation, Episode 6 (8.3)
Holiday episodes were never the most notorious running staple for The Big Bang Theory, but this episode became a classic when Howard decided to dress up like Sheldon for Halloween.
Unfortunately, the spot-on costume hurt Sheldon's feelings and prompted him and Amy to dress up like Howard and Bernadette and make unnecessary mean comments just to get back at them. Eventually, the couples reconcile and forgive one another when they have heart-to-heart talks about the insecurities that they made fun of.
The Change Constant, Episode 23 (9.2)
The final two episodes of the Big Bang Theory were also the two highest-rated episodes in the entire series and they revolved around the premise that Sheldon and Amy's research had won them a Nobel Prize. The first episode of the two-parter deals with all of the changes that are occurring in Sheldon's life with this newfound success and he can't deal with all of them at the same time.
That is, until he talks with Penny about how so much has changed over the 12 years they've known each other and that 'change' is actually a 'constant'. Sheldon accepts this and gets over his fear of change - as he finally steps onto the fixed elevator.
The Stockholm Syndrome, Episode 24 (9.6)
Only liars didn't cry at the end of this one. The perfect end to a phenomenal series saw the entire gang head to Sweden to watch Sheldon and Amy accept their Nobel Prize. Not only that, but Leonard and Penny reveal that they're pregnant and expecting a child.
During the ceremony in Sweden, Sheldon has constructed a very long and selfish speech about his prize, but puts it aside and instead thanks all of his friends for not only putting up with him but for loving him and inspiring him. The series ends with a final shot of the entire gang, back in the apartment where it all started, eating take-out food for one last time... and it all started with a big bang.