"There's a fine line between stupid and clever," and this, the mother of all mockumentaries, skirts it beautifully. Christopher Guest and Co. skewer the heavy metal/rock 'n' roll world so adeptly that when the film was originally released, many people didn't realize that it was a joke, and musicians from Steven Tyler to Eddie Van Halen prickled at how close to home it hit. Though fake documentaries are commonplace now, Spinal Tap is — and will always be — the one that turns the laughs up to eleven.