"Galaxy Quest," in which the has-been stars of cancelled cult sci fi-TV program are recruited by aliens for real-life star wars, is light but consistently entertaining fare. Director Dean Parisot has struck just the right note in poking fun but still paying homage to the science fiction genre and its devoted following. One need not be a Trekkie to find humor here as the movie delights in mocking show business and celebrity worship as well as the conventions of the genre. Tim Allen and Sigourney Weaver head a well-rounded cast that includes Alan "Hans Gruber" Rickman as a Shakespearean-trained actor unable to shake his career-making role as a Spock-like alien with a ridiculous prosthetic head. As supporting crew members looking for their moment to shine, Tony Shalhoub and Sam Rockwell steal nearly every scene.