A.O. Scott tells us that comedy is really just the many variations of one filthy joke told over and over again. The comedians try to outdo one another at telling the dirtiest, most extreme, most shocking and longest veresion.
Scott doesn't say what the joke is all about, except that the punchline is the title of the film, The Aristocrats, and that sometimes people have fainted at the end of the telling. The film itself is like a walk through comedy history, dissecting the same joke being told differently by generations and all sorts of comedians, including line drawned cartoon boys. The delivery and inflections change, but only this is assured: "The first is that what is funny cannot be explained, the second that it dies by repetition. Indeed, the more you hear the joke - and you hear it, in bits and pieces and all the way through, at least 60 or 70 times - the deeper you appreciate its peculiar fascination. And as various comedians reflect on its meaning and history...you come to understand the codes and customs of that peculiar guild that makes a living by trying to make the rest of us laugh."