A smart-alecky sendup of Hollywood in general and action films in particular, "Tropic Thunder" undeniably provokes quite a few laughs, but of the most hollow kind. Ben Stiller's star-laden farce makes every effort to be outrageous as it pokes knowing fun at a troupe of spoiled, self-centered actors who get more than they bargained for making a "Rambo"-like rescue drama in Southeast Asia. Apart from startling, out-there comic turns by Robert Downey Jr. and Tom Cruise, however, the antics here are pretty thin, redundant and one-note. But that note will strike a chord with a substantial, comic heat-seeking audience, particularly of the fanboy and combat-ready stripes, making for hefty late-summer biz. By TODD MCCARTHY @ Variety