For The Big Bang Theory's 200th episode, "The Celebration Experimentation," Sheldon gets a special surprise birthday. It becomes a bit too much for him to handle at first, but once Penny gives him a pep talk, he's able to enjoy himself in a celebration that includes Bat Man himself.

Hands down, the best episode of The Big Bang Theory this season was Season 9 Episode 11, "The Opening Night Excitation." Sheldon and Amy finally sleep together in an episode that balances humor and sweetness.

Sheldon and Leonard aren't thrilled, but Penny really loves the idea of a romance between Leonard's dad and Sheldon's mom. I mean, come on, how could we not be excited about that?

For some reason, Leonard's story arcs haven't felt very significant lately, other than his marriage with Penny. If there's anything we'd like to see next season, it's something of more substance for Leonard.

The best way to celebrate Valentine's Day? To crash your friends' live Fun with Flags episode wearing cupid outfits and throwing confetti at the camera. Leonard will apparently wear anything. Hey, he's a good sport.

Soon, we'll have a new addition to the Big Bang Theory gang! Howard and Bernadette learning that they have a baby on the way was another pivotal (and emotional) moment from The Big Bang Theory Season 9.

Sure, we love the friendship between Sheldon and Leonard, but this season's real BrOTP? Sheldon and Penny. Penny has learned to understand Sheldon in a way no one else can, and their friendship is wonderful (and funny) to watch as it continues to grow.

The guys plan a suprise bachelor party for Leonard on The Big Bang Theory Season 3, which involves a van that once belonged to Richard Fenyman, one of Sheldon and Leonard's favorite physicists. Unfortunately, they get a flat tire on the way to Mexico for their science themed trip, and struggle to change it, trying every scientific principle they can think of.

Somehow, Stuart became a character that become more creepy and more annoying as the season progressed. Sorry Stuart, but we really could have done without you this season.

It's a tough decision, but the favorite guest appearance on The Big Bang Theory Season 9 is definitely Christine Baranski as Leonard's mother. And this season, her interactions with Penny were basically priceless.

Sheldon making the decision to finally have sex with Amy is a big deal, but of course, the way he says it makes it sound a little less glamorous. "Then it's settled. Amy's birthday present will be my genitals."

There are so many fun and geeky moments on this show, but he best one of The Big Bang Theory Season 9 involves Wil Wheaton and a Star Trek uniform during the new Star Wars film. Bold move, Wil Wheaton. Bold move.

The beginning of this season was rough, with everyone fighting and basically acting miserable. The Big Bang Theory Season 9 Episode 2, "The Separation Oscillation" was the most negative, and generally uncomfortable to watch.