O'Brien tweeted the announcement Monday morning: "The good news: I will be doing a show on TBS starting in November! The bad news: I'll be playing Rudy on the all new Cosby Show."
The move was a surprise for those who expected O'Brien to end up on a big-four network, specifically Fox.
"In three months I've gone from network television to Twitter to performing live in theaters, and now I'm headed to basic cable," O'Brien said in a statement. "My plan is working perfectly."