If you are thinking this sounds like a spoof of Star Trek you're on the right track. Tim Allen (Home Improvement, Last Man Standing) adds his brilliant comedic contribution to this star studded cast which includes Sigourney Weaver, Tony Shalhoub, Alan Rickman, and Sam Rockwell. They are the aging stars of the one time hit TV series Galaxy Quest. None of them have worked much since the series ended and they make a meager living reprising their characters at various sci fi conventions, or worse, store openings. Tim Allen loves appearing for die hard fans of the show as "Commander Jason Nesmith", but none of the other cast members are very thrilled about these appearances, and resent the attention the "Commander" receives.
The cast finds a high quality mock up of the show's space ship at a store opening appearance, as well as some "extras" who are nothing if not 'in character' as members of an alien race seeking help from the famous crew.
Before they realize what has happened they find themselves in space on a real life adventure. This is a FUNNY movie which had me laughing to the end. I was really sorry when it was over, I loved it that much.

Really good watch, would watch again, and can recommend, especially for Star Trek fans.

This has a sufficiently high production value, but I think a lot of the budge went to hiring the cast, and building the locations, especially the ship. It's probably the chief reason why (at least I feel it is the case) people have wanted to do spoofs of Star Trek since the original series, but only "Galaxy Quest" and "The Orville" have really made the attempt. Usually the reaction is to take it in its own serious direction, like Babylon 5, and even "The Orville" lands in between.

I think my favorite aspect of this movie is that it's actually very similar to "The Invention of Lying" where not only does an alien race build a starship, hands it to Terrans, and then we just keep up the ruse so we can have a starship. While I think the more interesting aspect is the same things that we see in "Star Trek": the interactions between xenos and Terrans and the reflective aspects of humanity, the audience is quickly reminded that it's a comedy throughout the movie.

Everyone of the actors is funny, there's even a young Justin Long here, and while there is sufficient action / drama to move the story forward with some substance, it's the comedy that you're going to remember here. Alan Rickman and Tim Allen fighting, Sigourney Weaver translating from human to ship, and general awkwardness of situation.

It's a good watch, and I think that whether or not you're a fan of "Star Trek", then I think there is something at which you can laugh.

I usually struggle with comedy movies - but a combination of great casting; good, well-paced comedy writing and some lovely special effects from Stan Winston keep this rollicking along with loads of tongue-in-cheek swipes at the sci-fi genre (and "Star Trek" in particular) that is done in a sympathetic, engaging fashion. The "crew" are a bunch of washed-out actors doing the comic-con rounds with Tim Allen as the supercilious Captain: Alan Rickman - a wonderfully aloof thespian playing the disillusioned semi-crustacean ship's doctor; Sigourney Weaver as the buxom, but largely pointless "Tawny Madison" and Tony Shalhoub as the engineer on the "NSEA Protector". At one such event, they encounter the "Thermians" who need help battling the evil, all-conquering "Sarris". Having seen the telecasts of "Galaxy Quest" and treated them as actual historical documents the "Thermians" have built a real starship and hope the crew can be as true to their characters as they were to their scripts and save everyone's bacon... They are all on good form here, even poor old Sam Rockwell in the sort of Trekkie "red shirt" role (who expects to be killed at any moment). Perhaps not quite laugh out loud, but if you are a fan of this genre then you cannot fail to frequently raise a smile at the fight scenes that are comically staged; off course the captain's shirt gets ripped - and everyone finds a tiny bit of heroism in their persona. I loved it!