Rock and roll is so ridiculous, so over the top in its guitar anthem theatrics, that it should be a staple in the comedy canon. After all, there is nothing quite as amusing as a posturing performer shrieking inane songs about sex and drugs in tight pants that leave nothing to the imagination. Unfortunately, most attempts to mix music with mirth come up substantially short (last year's lame Rocker being a prime example). However, if you go back 25 years, you'll find one of the wittiest, and wisest films about being a band ever created. As a true humor masterpiece, This is Spinal Tap has few motion picture peers.

As part of the promotion for their new album, Smell the Glove, the main members of UK metal icons Spinal Tap -- guitarist/vocalist David St. Hubbins (Michael McKean), Nigel Tufnel (Christopher Guest), and Derek Smalls (Harry Shearer) -- have decided to embark on a U.S. tour. While still mildly successful in Europe, the middle-aged group, known for consistently losing a series of drummers to freak accidents, hopes to rekindle their popularity. As part of the publicity parade, filmmaker Marty DiBergi (Rob Reiner) will be following the band, documenting their attempts to reconnect with an American audience. Sadly, forces outside the band threaten the entire production, especially when David's girlfriend Jeanine (June Chadwick) arrives, offering her out of touch ideas about Tap's direction over the vehement objections of manager Ian Faith (Tony Hendra).

It's rare when a film is the best representative of several significant genres -- but that's This is Spinal Tap. It's the best mock-documentary ever made. It's the funniest spoof of heavy metal ever conceived (so truthful that many bands swear it was their career that the narrative borrowed). It's the best work in director Rob Reiner's scattered oeuvre and the most insightful satire ever attempted by Guest and his merry band of improvisers. Along with a soundtrack that takes such cock rock showboating down several sensational notches and a visual inventiveness that confirms its "authenticity," Tap transcends its make-believe bumbling to become a true comedy classic. Besides, this is one of the few laughfests where the actors are an accomplished live band as well (the stars composed and played all the songs on the soundtrack).

Authenticity remains the key to Tap's success, the notion that what we are watching may actually be true, no matter how silly or strange it seems. McKean, Guest, and Shearer never wink at the camera, acknowledging that this is all just a great big put-on. Instead, they do their deadpan best to give each moment the most realistic reading possible. Even when they're discussing obvious joke ideas like a Jack the Ripper rock opera or contemplating a miniaturized Stonehedge (in one of the movie's most memorable sight gags), their accurate responses produce leagues of laughter. Equally hilarious are scenes where the individual members discuss their hopes and dreams (including Nigel's collection of guitars, and his amplifiers that "go to 11").

In fact, This is Spinal Tap rarely makes a misstep on its way to cinematic immortality. Cameos by stars like Robin Williams, Billy Crystal, Paul Schaeffer, and Fran Drescher only add to the anarchy, and the Yoko-like confrontations between the band and David's ditzy gal pal Jeanine are rife in their discomfort. Sure, there are things that seem quaint and nostalgic now (one wonders what the Tap talent would do with cellphones, CDs, MP3 players, and file sharing), but making fun of something worth mocking is indeed timeless. No matter the hair style, musical form, or era explored, rock and roll really lends itself to farce. This is Spinal Tap illustrates this point perfectly.

Of special note is the new Special Edition DVD for the film, which features more time in extras than the entire running time of the film. Over an hour of outtakes could effectively make a new film, and a commentary track features the original cast -- in character -- discussing the movie ostensibly about them. Talk about mud flaps! The DVD adds more making-of featurettes and a bonus DVD featuring Spinal Tap playing the 2007 Live Earth concert, and more.