Galaxy Quest. Why did I not learn of this very funny movie until last week? (Thank you, scifan!) If you like Star Trek (or perhaps especially if you don't!) you're bound to enjoy this affectionate send-up of cheesy sci-fi TV shows, conventions, and fandom. The ensemble cast is delightful, and no cliché is left unmocked.
Part of the spoof's effectiveness is the contrast between low-budget TV production values and spectacular modern visual effects. To say more would be a spoiler. Yet, hiding under the satire is a decent sci-fi tale, with credible villains, victims, and heroes.
Bound to become a cult film.