"The Aristocrats" (also called "The Debonaires" or "The Sophisticates" in some tellings) is a taboo-defying off-color joke that has been told by numerous stand-up comedians since the vaudeville era. The joke was the subject of a 2005 documentary film of the same name. It received publicity when it was used by Gilbert Gottfried during the Friars' Club roast of Hugh Hefner in September 2001.
Gilbert Gottfried knows what "The Aristocrats" is.