I don't know which is funnier - Tropic Thunder, a comedy about a bunch of actors making a Vietnam war movie ... when their director decided to dump them in the middle of a real one, or Rain of Madness: a (viral?) mockumentary about the craziness of the making of the movie inside the movie.
Confused? That's okay - just enjoy the trailer at Always Watching: http://www.alwayswatching.org/news/tropic-thunder-rain-madness-mockumentary
I predict great concept, but lousy execution ... on both films.