Galaxy Quest is a TV science fiction series that tells the story of space NSEA protectors 20 years ago. It was discontinued in 1982. Nearly 20 years later, Jason (Tim Allen), who plays the commander, Alexander (Alan Rickman), who plays the doctor, and Gwen (Sigourney Weaver) and other actors reunited to participate in a series of fan meetings and commercial activities. During this period, a group of weird fans who called themselves Semians followed Jason to his home. The tired Jason found that these Semians were not crazy fans, but real aliens! After watching Galaxy Quest, the Semians, who had no deception ability, thought that Jason and others were real space heroes. They were defeated in the duel with the cosmic villain Sarris, so they went to Earth to seek help from the protectors. Jason and Alexander and other crew members pretended to help the Semians fight against the evil forces of the universe...