In the pantheon of alien-oriented sci-fi movies, a qualifier for true greatness is the caliber of the extraterrestrial. The more unique and strange they are, the more likely audiences will still be talking about them decades later. Case in point: Galaxy Quest. Celebrating its 20th anniversary this year, the beloved satire of low-fi, space-exploration television shows and their egocentric human casts works for many reasons, including a brilliant script and pitch-perfect performances.