This Is Spinal Tap

(officially spelled with a non-functional umlaut over the letter 'n' and dotless 'i') is a 1984 mock rockumentary directed by Rob Reiner and starring members of the fictional heavy-metal/hard rock band Spinal Tap. The film satirizes the wild personal behavior and musical pretensions of hard-rock and heavy-metal bands, as well as the hagiographic tendencies of rockumentaries of the time. Despite Reiner and the three main stars being credited as the writers of the film, much of it was ad lib,... full article at wikipedia