Grease-painted demons haunt my every waking second.
I've found a few sites that have information on the ancient origin of clowns. The last link is a treasure trove of Usenet ranting.
This guy says the origin clowns are slur against Irish/Scottish folk. Yep. That's what he said.
I also found a short history of American tramp clowns. And, no, they didn't originate among a race of garbage eating mutants. So much for that theory.
And remember, somewhere there's a factory that makes clown shoes.