Galaxy Quest(1999)

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.