Have you heard about The Aristrocrats? This documentary, produced by Penn Jillette (of Penn and Teller), features over 100 famous comics (including Robin Williams, Bob Saget, Chris Rock, and George Carlin) telling a single legendary -- and very very filthy -- joke. The film's tagline: "No nudity. No violence. Unspeakable obscenity."
Here's a clip of the South Park version. Warning: Very very filthy. Definitely NSFW!
And a SFW New York Times review of the film.
I first heard this joke about fifteen years ago when my very funny friend Joe Monti, a magician and comedian, told it to me at the Magic Castle. His delivery was exceptional; I literally haven't ever laughed so hard at any other joke, ever. I'm talking incapacitating laughter, continuing for a good five minutes.
If you have a high tolerance level, the potential is extraordinary. I'm DYING to see this...