A big (bang) guest star has signed on for the Grey's Anatomy season finale.

According to Michael Ausiello, a CBS sitcom star has signed on to appear in the the May 14 episode.

Kaley Cuoco, the lovely leading lady on The Big Bang Theory, will star in the finale as... someone. The actress admits she actually has no idea about the character she'll portray.

"I am working on Grey's Anatomy next week," Cuoco said. "It is a big ol' secret. I have no clue what I am doing. I swear on my life that I have no idea what I am playing because it is the finale and they are keeping it under wraps until the last possible moment."

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.