The apocalypse comedy "This Is the End"
is completely fictional. Not that you'd think it was a documentary given that it follows a group of people trying to survive a literal Hell on Earth during the Rapture, but those people are all based on real celebrities, namely James Franco, Seth Rogen, Jonah Hill, Craig Robinson, Danny McBride and Jay Baruchel. Very loosely based on, that is. Parodies, really. Or self-parodies since they're all played by the actual actors.
It's not uncommon for celebrities to play this sort of mock version of themselves on TV and in movies, often playing up some negative trait to make fun of their notoriety. Cameos are more common and usually entail the person coming off as a jerk. Occasionally, though, the part is much bigger.
Here, we highlight 13 of the best performances of actors in larger roles, either the lead or supporting character, as "themselves."