By Grabthar's Hammer

We've just spent the last hour and a half giggling away at Galaxy Quest about the washed up stars of a fictional 1978-1982 TV series called "Galaxy Quest" (a parody of the television series Star Trek) who've spent the last seventeen years on the fan convention circuit and are now contact by real aliens who, owing to a misunderstanding, think they're a real starship crew and want their help to save their planet.

Very funny, very well done, highly recommended.