"The Big Bang Theory" is about to celebrate its 200th episode with season 9 episode 17, aptly titled "The Celebration Experimentation." The episode's story, as per Entertainment Weekly, will focus on Sheldon Cooper's (Jim Parsons) birthday festivities and one of the main surprises to his party is the arrival of Adam West.

West will be portraying himself. The actor is known for playing Bruce Wayne aka Batman in the 1966 live-action TV series and also voiced a caricature of himself, known as Mayor West, in the Seth McFarlane cartoon series "Family Guy." 

According to the report, Sheldon and his peers consider Adam West one of their heroes, given that the latter portrayed Batman for a long while on television. This may be considered similar to how Sheldon and his friends looked up to Professor Proton (Bob Newhart).

However, the arrival of West isn't the only surprise coming for the special episode as several guest stars who haven't been on the show for some time will be making a comeback.

TVLine reports that four other characters will be making an appearance in the episode. Returning to "The Big Bang Theory" is Sara Gilbert, who played Dr. Leslie Winkle. Gilbert departed from the series after the third season to focus on another project and because the writers generally had no plan at the time regarding where to take her character.

Dr. Beverly Hofstadter (Christine Baranski) will be making an appearance, as well as Barry Kripke (John Ross Bowie) and Wil Wheaton, former "Star Trek" star. Wheaton has played himself on the show several times, initially as a rival to Sheldon Cooper until the two reconciled and are now considered best friends.

However, the official synopsis of the episode has been kept a secret. CBS has officially kept the synopsis under wraps, ensuring that even the fans will be surprised of what the special guest stars will have planned for Sheldon's birthday. 

"The Big Bang Theory" season 9 episode 17, "The Celebration Experimentation," airs this Feb. 25.