zap.
A friend recently fanned the flames of my obsession with figuring out what would happen if an actor in a movie could rent a movie and see themselves in it. Or is it that I wonder if each movie is simply set in an earth-like place, but obviously one where certain films don’t exist?
Bill Murray and Woody Harrelson were both in the 1996 film Kingpin.
In the movie Zombieland, Woody Harrelson plays a character named Tallahassee, but Bill Murray plays himself. Tallahassee tells Bill Murray that he’s seen every film he’s ever been in. It then follows that he would have seen Kingpin, in which he stars, alongside Bill Murray.
ALL I’M SAYING is that this is impossible. Kingpin must not exist in that world.

OK.Why must this go on and on?
In that movie’s universe, Woody Harrelson IS NOT Tallahassee. Therefore, Tallahassee could have seen Kingpin as it stared Woody Harrelson and Bill Murray. Not a problem.
To illustrate Cate’s point, I refer you to Holden’s comment in Jay and Silent Bob Strike Back, in which he opines that “Affleck was the bomb in Phantoms”.
Evidently, the character Holden can watch (and indeed has watched) a movie with Ben Affleck in it — their only relation being that they bear a striking resemblance to each other.