(Starring Tim Allen and Sigourney Weaver.)
A send-up of various (but mostly Star Trek) space science-fiction TV series, that also stands up rather well as a science-fiction film in itself. You don't need to know the shows that it sends up, to enjoy the film. And you can view it as a comedy, and/or a science-fiction.
The story begins with some has-been science-fiction show TV stars attending yet another fan convention, with bad grace. They get mistaken for real outer space heros by some naive aliens who're on the brink of total annihilation, desperate to find someone to defend them, and seek out the TV stars.
Fans of the original Star Trek TV series will recognise various parts of the plots, some of the location shots, and some of the antagonism between the stars. It's a fun movie, with plenty of enjoyable and amusing moments.