The name of the movie is : The Aristocrats
Comedy veterans and co-creators Penn Jillette and Paul Provenza capitalize on their insider status and invite over 100 of their closest friends--who happen to be some of the biggest names in entertainment, from George Carlin, Whoopi Goldberg and Drew Carey to Gilbert Gottfried, Bob Saget, Paul Reiser and Sarah Silverman--to reminisce, analyze, deconstruct and deliver their own versions of the world's dirtiest joke, an old burlesque too extreme to be performed in public, called "The Aristocrats."
The joke involves a person pitching an act to a talent agent. Typically the first line is, "A man walks into a talent agent's office." The man then describes the act. From this point, up to (but not including) the punchline, the teller of the joke is expected to ad-lib the most shocking act they can possibly imagine. This often involves elements of incest, group sex, defecation, necrophilia, bestiality, and various other taboos.
The joke ends with the agent, shocked and often impressed, asking what the act is called. The punchline of the joke is then, "The Aristocrats".
http://en.wikipedia.org/wiki/The_Aristocrats_%28film%29
