Galaxy Quest Reviews
It's actually a pretty adorable parody of Star Trek in which washed up actors playing the fan club circuit do get roped into an adventure - but much of the wit comes from the unlikely circumstances through which everything plays out just like an episode of Star Trek - and the spectrum of reactions that the actors have toward this.
It's entirely unlike "Spaceballs". In that movie, Mel Brooks just used Star Wars as a canvas on which to put his shtick. Galaxy Quest is done from the inside - it was clearly written by big Star Trek fans who simultaneously love the show while being acutely aware of its absurdities, and who have a similar love and amusement for the Trekkies who take their love of the show a little too far.