5. Bruce Willis
In the last few seasons of the show, cameos on Friends became an almost weekly event. George Clooney, Brad Pitt, Julia Roberts and a bunch of other actors who were not in the Ocean’s Eleven movies made appearances. Bruce Willis was one such actor, thanks to his pal Matthew Perry. They’d both been in the movie The Whole Nine Yards. Perry and Willis made a bet about the success of the film. If Perry won, Willis would have to appear on Friends for no pay. Perry won the bet so Willis made a pro-bono cameo.