humor-hauler

One who insists on carrying on with a funny concept, item, or subject to the point where it has lost all of its humorous qualities.

Nick: Dude, can you believe Julian? He's been rambling on about that punchline forever! I mean seriously, its not even funny anymore.
Courtland: I know! He's such a humor-hauler!

by XC Penguin August 8, 2010