Ferrell joined O'Brien in February for his final "Late Night" show in New York. Now the actor-comedian will help O'Brien kick off his tenure on "Tonight" in Los Angeles.
Pearl Jam will be the first band on O'Brien's show, playing songs from an upcoming studio album, NBC said Monday.
O'Brien takes over the late-night show on June 1, after Jay Leno wraps up his 17-year run as "Tonight" host on May 29. Leno is moving to a daily prime-time series for NBC in the fall.
Copyright 2009 The Associated Press.