What is the world's funniest adult joke?

The most famous dirty joke is "The Aristocrats." The joke is believed to have originated in the vaudeville era and has been told and retold ever since.

The setup for the joke is nearly always the same, a man and his family walk into a talent agency and audition with a series of obscene acts. At the end of the joke, the agent asks what the name of the act is and the man responds with the punch line, "The Aristocrats."

What makes the joke famous lies in the individual comic's telling of the middle of the joke, as he describes the act. The act is usually immoral, indecent and involves describing scenes of sex and incest mixed with the most gross and disgusting things that the comic can think of.

The joke received publicity when Gilbert Gottfried told his version of the joke at the Friar's Club roast of Hugh Hefner in 2001 and had a documentary film, titled "The Aristocrats," made about the joke in 2005.