How does a simple idea end up becoming a signature joke? Why do some comics embrace profanity while others avoid it? Do audiences really matter? In this one-hour HBO special, four stand-up legends--Jerry Seinfeld, Chris Rock, Ricky Gervais and Louis C.K.--answer these questions and more as they let their guards down in an intimate, unscripted conversation about what it means to be a comedian, and how far each has been willing to go to push the limits of taste and originality for a laugh.