This Is Spinal Tap is an American 1984 rock and roll musical mockumentary directed by Rob Reiner about the fictional heavy metal music band Spinal Tap. The movie satirizes the wild personal behavior and musical pretensions of hard rock and heavy metal musical bands, as well as the hagiographic tendencies of rock documentaries of the time.
Reiner and the three main actors are credited as the writers of the movie, based on the fact that much of the dialogue was ad libbed by them. Several dozen hours of footage were filmed before Reiner edited it to the released movie. A 4½ hour bootleg version of the movie exists and has been traded among fans and collectors for years.