Janitor

He mops the halls of Sacred Heart hospital with the air of a man running his own private kingdom, and his chief hobby is tormenting J.D., the terrified new intern, with escalating lies, grudges, and schemes that never quite add up to a reason. Nobody knows his name. He seems to prefer it that way.

The joke is that a hospital comedy keeps handing its best deadpan material to a man whose job title is his only identity. Neil Flynn plays every absurd vendetta with total sincerity, so the character becomes funnier the less sense he makes, and stranger the more you wonder if he's making sense of you.