Big things have been happening on The Big Bang Theory, and now cast and crew are getting ready to celebrate a major real-life milestone.

After nine and a half seasons of geeky madness, The Big Bang Theory episode 200 airs tomorrow night on CBS. The episode, titled “The Celebration Experimentation,” will guest star Adam West (of 1960’s Batman fame) as well as Christine Baranski as Leonard’s mother, and Sara Gilbert as Leonard’s ex-girlfriend Leslie Winkle.

But in spite of the Leonard-centric guest stars, The Big Bang Theory‘s 200th episode looks like it’s really all about Sheldon.

The major milestone comes on the heels of several pivotal moments in The Big Bang Theory‘s history. In season 9 alone, Leonard and Penny finally got married, Sheldon and Amy broke up, got back together, and engaged in the long-anticipated coitus, and just last week, Bernadette announced her pregnancy.

So it seems appropriate that “The Celebration Experimentation” will focus on a significant, but less momentous moment in the lives of the geeky gang — though in the words of Simon Helberg, Sheldon’s birthday is going to be a “bizarro,” Comic-Con style bash.

Part of the wildness will come from Adam West, who says that he is playing “a little cuckoo version of myself… I get to insult a lot of big stars!” the actor laughs.

The origins of the madness are evident in a few clips from The Big Bang Theory episode 200, in which the wheels of Sheldon’s party are set in that reluctant, “this-might-be-a-terrible-idea” kind of motion.

And just in cast you felt like celebrating in the most Sheldon-y way possible, The Big Bang Theory has provided fans with 200 minutes of Sheldon proclaiming his catchphrase, “Bazinga!” (We dare you to watch for more than thirty seconds.)

Happy birthday, indeed.

The Big Bang Theory episode 200, “The Celebration Experimentation,” airs Thursday Feb. 25 at 8:00 p.m. on CBS.

How do you think Sheldon’s big birthday will play out on ‘The Big Bang Theory’?