It's hard to overstate the impact of This is Spinal Tap (96 percent) on both cinema and pop music. Though it wasn't the first mockumentary, Spinal Tap was such a perfect embodiment of the form that the fake doc became a subgenre onto itself. Then there's the sheer accuracy of the whole thing; Spinal Tap was so merciless and informed as a send-up of the rock universe that, according to This is Spinal Tap: The Official Companion, rock stars like Sting, Yes' Jon Anderson, and Guns 'n' Roses' Slash have all commented on the starling resemblance to their experiences. (It's also rumored that Steven Tyler and Eddie Van Halen didn't get that Tap was supposed to be a comedy.)

Spinal Tap is the story of a witless, second-string British hard rock band (played by Michael McKean, Christopher Guest, and Harry Shearer) in the midst of a sharp decline. A tour to promote their latest album, Smell the Glove, has hit a number of snags, including low ticket sales, concerns that their new album cover is sexist (not sexy!), internal tensions, malfunctioning and/or poorly designed stage props, and the fact the band's drummers consistently die under bizarre circumstances. Director Rob Reiner also stars as a filmmaker shooting a documentary about the band; in interviews, he gleans profound insight into why the band's amps go up to 11, and how much more black one of their album covers can be. (The answer is none. None more black.)

Spinal Tap: Stonehenge -- No one knows who they were...or what they were doing.

Perhaps the most undervalued aspect of the film is that Spinal Tap's songs are good. Gleefully stupid, filled with profane double entendres, such cuts as "Tonight I'm Gonna Rock You Tonight," "Big Bottom," and "Heavy Duty" may not be in the same league as AC/DC, but they're far more entertaining -- and tuneful -- than your average Whitesnake record. "It stays so wickedly close to the subject that it is very nearly indistinguishable from the real thing," wrote Janet Maslin in the New York Times.