Galaxy Quest: Junior Novelization

A group of has been TV performers cash-in on their past glory by attendings Sci-Fi Conventions and signing memorabilia for their still enthusiastic fans - that is until real aliens from Thermia, who have mistaken the TV show's episodes for reality (referring to them as the 'Historical Documents'), appear at a convention to ask the former crew of the N.S.E.P. Protector for help against a malignant enemy named Saris, who has already wiped out the rest of the Thermians' squid-like species.