It will be spot the celebrity when Entourage opens today.
Among the actors and celebrities playing themselves in cameos are Gary Busey, Mike Tyson, Mark Wahlberg, David Spade, Tom Brady, George Takei and Ed O'Neill.
There are also some big names - like Billy Bob Thornton - who are in character.
The HBO TV series on which Entourage the movie is based, regularly featured stars playing themselves, just not this many at once.
The cameo has a long history in Hollywood. Alfred Hitchcock made cameo appearances in 39 of his 52 films. Jim Parsons appeared in the 2011 Muppets film and Alice Cooper made a cameo in Wayne's World, in 1992.