'The Big Bang Theory' Season 9 Episode 17 Spoilers: Sheldon Gets A Suprise Guest in 'The Celebration Experimentation'

"The Big Bang Theory" season 9 episode 17 isn't any normal episode - it's the CBS comedy's 200^th episode for the whole series - and they're pulling out all the stops to make "The Celebration Experimentation" go out with a Big Bang!

 Congratulations to the #BigBangTheory for 200 episodes! Now let's eat cake!!

A photo posted by The Big Bang Theory (@bigbangtheory_cbs) on Feb 20, 2016 at 10:18pm PST

According to International Business Times, a few characters will be making a return, while a guest star joins the rest of the gang for the night.

Most of the details for season 9 episode 17 are being kept secret - but even with a stripped down sneak peak on the episode's plot, they've managed to reveal a huge bomb: Sheldon (Jim Parsons) gets the surprise of his life when Adam West shows up at his birthday party!

200. odcinek 'Teorii wielkiego podrywu'! https://t.co/l4xOe1rpAU #ccpl #bbt #bigbangtheory #celebration #adam #west pic.twitter.com/4yWIsNbwQR — Comedy Central PL (@ComedyCentralPL) February 21, 2016

Adam West gained much popularity for being the first actor to ever portray a live-action Batman back in the 1966 series, "Batman."

Entertainment Weekly reports that while West would be playing himself, odds are that he'll be seen as a hero - Bruce Wayne, no less - in the eyes of Sheldon, Leonard (Johnny Galecki), Howard (Simon Helberg) and Raj (Kundal Nayyar).

The Big Bang Theory festeja sus 200 episodios con Adam West https://t.co/VpSCbvobzn #Cine pic.twitter.com/GeZBCqPRz7

— LA 100 (@la100fm) February 13, 2016

As for the returning characters - Christine Baranski will portray Dr. Beverly Hofstadter (Leonard's mom), John Ross Bowie will portray Barry Kripke, and Sara Gilbert to portray Leslie Winkle. Wil Wheaton will also appear on the show to play himself.

Leslie Winkle's return will be her first since leaving the series back in season 3, when Leonard was busy looking for a rebound after his first break up with Penny (Kaley Cuoco).

"The Big Bang Theory" season 9 episode 17, "The Celebration Experimentation," airs on Thursday at 8PM ET on CBS.