Erick Von Erich wrote:
Would you count Cliff Clavin and Eddie Haskell? In both cases, I'd say they were recurring characters who got promoted.
In Cliff's case I guess it depends on if his name was always part of the opening credits or not. I don't know offhand.
John Ratzenberger as Cliff Clavin wasn't in the opening credits of the first season of "Cheers", but was for every season thereafter. In the first season he was in the ending credits, usually if not always having a credit alone rather than sharing the title card with another performer. The show ran for 271 episodes and he appeared in 270 of them. The only one he didn't appear in was episode 4 of season 1. Despite not appearing, he was still included in the ending credits, suggesting both that a scene with him was shot, or at least originally scripted, but was edited out and that, even at that early stage, John Ratzenberger was considered a regular member of the cast as Cliff.