Movie actors become celebrities, and then we make movies about celebrities because people like that. Also, Hollywood screenwriters can feel very comfortable writing about things they know firsthand, which is Hollywood. The result is quite a few movies about movie actors, which you get movie actors to play. The most obvious example of an actor playing himself is Being John Malkovich, because who else would they get to play the part of Malkovich? But things get even more meta with Robert Englund doing two roles in the 1994 movie Wes Craven’s New Nightmare.
In New Nightmare, Freddy Krueger invades our world and terrorizes the actors and crew who helped make the Nightmare on Elm Street films. Englund reprises his role as the iconic killer, but as this movie is set in the “real” world, he also plays himself, the actor who played Freddy Krueger.
Can it get more meta than that? You’ll have to check out the list of 17 actors who played themselves to find out.