Shot with simple home-video cameras wherever the filmmakers could catch up with their colleagues, this doc toys will the nature of humour while indulging in the most childishly vulgar smut imaginable. Actually it's beyond vulgar, because the main point of the joke is to make it as outlandishly tasteless as possible. And then some. Producer Penn Jillette (of Penn & Teller) describes it as jazz: "It's about the singer, not the song". It's not where you're going that's important;it's how you get there. And as Carlin observes, its power is in the way "it plays with people's danger zones".

As each comic embellishes the joke in their own inimitable way ("And there's a dog," shrieks Diller). It's so insanely shocking that we can't breathe, and people around us in the cinema are laughing at very different bits. "The joke kind of makes its own gravy," McKean adds, with a particularly bad metaphor. Highlights include family entertainer Sagat's astonishingly vile version, Pollak's hilarious Christopher Walken impersonation and Fisher's Hollywood royalty rendering.

This is the simplest of docs, production wise. It merely points the camera at talented, funny people and lets them tell the joke, talking around it, trying to understand its longevity. We even get a clip of Gottfried daring to tell it to a room full of comics just weeks after 9/11, a time when people were afraid to laugh, and they're literally falling out of their chairs. But the film's bracing simplicity is deceiving; Penn and Provenza sifted through hundreds of hours of tape to compile these 92 minutes. Which means we have an even more astonishing DVD on the way.

very strong themes and language

1.Aug.05