In the case of the Coach on CHEERS we had a contest in a writers room to see who could pitch the dumbest Coach joke. One day we were faced with the following set-up: Sam is in his office. The Coach comes in to say he’s got a call. Jerry Belson is one of the funniest people I’ve ever met. He pitched this:
COACH: Sam, there’s a little black man in the bar who wants to speak to you.
SAM: No Coach, that’s the phone.
In case that wasn't clear from my description of it (read the post), that wasn't a line that was used or intended to be used on the air; Belson was pitching a line that would make the Coach even dumber than he normally was.
Incidentally, someone should compile a list of all the shows and movies contributed to by Jerry Belson as an uncredited re-writer. After he and Garry Marshall broke up, in addition to his credited work, Belson has done a lot of uncredited consulting, re-writing and polishing work. For example, he wasn't credited on Cheers but he did work on it; James L. Brooks brought him in to do some uncredited work on some Simpsons episodes, including their first flashback episode, "The Way We Was" (Belson was brought in because of his experience with The Dick Van Dyke Show and their fifty kajillion flashback shows); he did some uncredited work on the mostly-uncredited script of Close Encounters of the Third Kind, and so on.