Happily for us, director Reiner, who developed the underlying story line with Guest and former Credibility Gap pranksters McKean and Shearer, stays squarely on the right side of the line, even as his writer-actors remain hilariously trapped on the other side. In lieu of a formal shooting script, the quartet created an extensive and detailed band history ripe with the sort of dead-pan detail that hard-core rock historians and screwball aficionados will savor on countless replays; with the three Tap members also musicians themselves, the "band" developed its stage act under the unsuspecting noses of L.A. club denizens, who accepted them as just as loud, flashy, sexist, and obvious as any other mullet-tressed, leather-garbed brigade of guitar slingers, circa 1984. The resulting footage thus manages to lob its punch lines and build its characters (including some thinly veiled character assassinations of various industry folks) with a loose, tossed-away verve rooted in the improvisational approach. This Is Spinal Tap remains the funniest, and most truthful, look at rock culture ever filmed and a personal best for all involved. --Sam Sutherland