Long after their show has gone off the air, GalaxyQuest's cast drag themselves numbly to conventions, where geeks in space suits assault them with technical queries. Turns out a few of the dweebs are actual aliens, who believe the show's actors are just the astral heroes needed to rebuff an attack on their planet. There's a bit of humor in the spectacle of Tim Allen as a Shatnerized action figure and Sigourney Weaver as a blond bimbette, but the premise--familiar from the 1986 comedy !3 Amigos!--needs more ingenuity to enliven it than anyone here could muster. In this space epic, no one will hear you laugh.
--By Richard Corliss