Of the litany of famous guest stars on Friends, Bruce Willisstood above the pack, both in terms of shock value and the quality of his performance. When the long-running sitcom managed to nab the talents of the Die Hard and Sixth Sense star, it proved that it was every actor's dream landing spot, even if they were only on for one episode. Friends had such a strong influence on culture at large that Willis, a major star who would justifiably command a hefty price tag, worked for free when he appeared as Paul Stevens in Season 6, the father of Ross' (David Schwimmer) girlfriend at the time, Elizabeth (Alexandra Holden). Well, there's a catch to this story, as this memorable three-episode arc only occurred because Willis lost a bet to his co-star in the 2000 crime comedy, The Whole Nine Yards, Chandler Bing himself, Matthew Perry.