Tropic Thunder ***

A big-budget sendup of big-budget action movies, "Tropic Thunder" takes some chances spending so much money to ridicule big movies, narcissistic actors, studio bosses (wait till you see what they did to Tom Cruise), and pea-brained agents. Thank goodness they, or rather, Ben Stiller, who has directing, writing and producing credits, succeed.

The cast is top drawer. In the group of actors that finds themselves in a real war, besides Stiller, there's Robert Downey Jr. as an Australian actor of some renown who has had his skin darkened so he can play a black soldier, Jack Black as an actor with some controlled-substance issues, rising comic star Jay Baruchel, and Brandon T. Jackson as Alpa Chino, the real man of color in the squad. Through in Nick Nolte as a demented author, Steve Coogan as the hapless director, and the aforementioned Cruise as a studio exec, and there's every reason to expect good things.

By its very subject matter, this is a narcissistic movie about movies and the movie industry, but in a day of E! channels and box office numbers reported like sports scores, American audiences, at least, can keep up. And there's plenty of explosions for the teenboy fans. It's a good romp, and a satisfying summer popcorn flick.

Rated R. 107 minutes. Ben Stiller - Director / Writer (screenplay) (story) / Producer, Justin Theroux - Writer (screenplay) (story), Etan Cohen - Writer (screenplay), Stuart Cornfeld - Producer, Eric McLeod - Producer, John Toll - Cinematographer, Theodore Shapiro - Composer, Jeff Mann - Production Designer, Greg Hayden - Editor. Distributed by Dreamworks Distribution.

Principal actors: Ben Stiller, Jack Black, Robert Downey Jr., Nick Nolte, Steve Coogan, Danny McBride, Bill Hader, Jay Baruchel, Matt Levin, Andrea De Oliveira, Reggie Lee, Matthew McConaughey, and Tom Cruise.