Try to avoid reading too much into this movie. I've had a lot of its gags spoiled for me, so try to see it (at 15) with a fresh face. Like mockumentaries that would follow, what makes "Spinal Tap" work so well is the commitment the "band" makes. The accents, the gum chewing, the ego trips. And they're all so dumb with just idiotic filthy lyrics, and everyone gets to be in on the joke. It's a fast trip, made me laugh fairly often, and even if it is a little predictable the excellent humor it presents overshadows it.