Charlie Callas is a hysterical comic "known for his rubbery face, trademark nervous chattering and dark comedy" according to Wikipedia.
I happened upon this clip while looking (in vain) for Callas' final appearance on The Tonight Show in 1983. During that appearance - I am told - Callas was bombing badly and, out of desperation, shoved Johnny out of his chair and onto the floor to get a laugh. He was IMMEDIATELY banned from the show for life.
As a result, you don't see Charlie much on TV anymore. Too bad, he was a funny guy.