I just saw an early Sunday morning screening of the documentary feature The Aristocrats. Oh. My. God. The subtitle of the film is "No Nudity. No Violence. Unspeakable Obscenity." for good reason.
The idea of the documentary is that there is a joke that has been doing the rounds for decades, a joke that is so unspeakably filthy that comedians tend to tell it to each other, and it rarely gets told to an audience. The other important aspect of the joke is that only the front set-up and the closing punchline are established, and the middle of the joke, the body of it, is usually ad-lib. Oh, and is supposed to be full of the dirtiest things you can imagine.
One of the funniest aspects of the film is seeing famous comics, like Paul Reiser, step outside their normally clean image and tell this disgusting joke. I especially loved a magician/comedian who told the joke as a card trick, using individual cards or sometimes the whole deck, to highlight parts of the joke. I have no problem with filthy jokes, but this film is not for those who are easily offended!
I think it's ending its run here in Sydney, but if you don't mind dirty jokes then I recommend it.