The popular television series Friends has been graced by the presence of many well-known Hollywood stars in guest appearances. One of these stars was Bruce Willis, the renowned Hollywood actor known for his role in Die Hard. During Friends season 6, Willis had a three-episode story arc that remains one of the most memorable guest spots in the show's ten-season run. In Friends, Bruce Willis portrayed the character of Paul Stevens, the over-protective father of Elizabeth, who happened to be the much younger girlfriend of Ross Geller, played by David Schwimmer.

However, the story behind Willis' appearance on the beloved 90s sitcom is quite interesting.

Matthew Perry, the actor who played Chandler Bing on Friends, had previously worked with Bruce Willis in the film "The Whole Nine Yards." After the completion of the film, Willis made a bet on its success. If the movie performed well at the box office, Perry challenged him to make an appearance on Friends.

Willis, not holding high hopes for the film's box office performance, took the bet and unfortunately lost. To everyone's surprise, "The Whole Nine Yards" went on to make a staggering $106 million worldwide and became the number one movie in America for three consecutive weeks. This meant that Bruce Willis had lost the bet and was obliged to join Friends for a short period of time, as agreed.

During its run, Friends became famous for its guest appearances by popular celebrities. Brad Pitt, Julia Roberts, and Robin Williams were just a few of the many well-known faces from the 90s who made cameo appearances on the sitcom. Bruce Willis' inclusion in the series added to its already star-studded list of guest stars.