From way back. Roseanne Rosannadanna on Weekend Update. She would start replying to the topic at hand and then quickly go off on some disgusting but hilarious tangent. A toenail found in her hamburger, or a boil that needed to be lanced, etc.
I also always liked those pre-recorded pieces that featured practically the entire cast, such as for a Various Artists Christmas Music album, or recently, celebrity auditions for the latest Star Wars.