Eight-medal Beijing Olympic swimming champ -- and big "Entourage" fan -- Michael Phelps recently stumbled upon the set of HBO's hit series while it was filming in Midtown Manhattan. Seizing a great opportunity, series producer Doug Ellin immediately wrote the star athlete into the show with a cameo opposite the show's Kevin Connolly.

Phelps is a wanted man these days: He's been swarmed with commercial and showbiz offers, and will be hosting the season premiere of "Saturday Night Live" on September 13. The fifth season of "Entourage" kicks off Sunday, September 7 on HBO, with Phelps' appearance coming in a future episode.