War is hell. Hollywood satires, more so.

Last week it was Pineapple Express. This week it's Tropic Thunder. Hope this is a trend; Hollywood should have more movie titles that sound like flavors of juice smoothies.

Speaking of Hollywood, it's always risky business to make a satire that skewers the movie industry. Most prior attempts are pretty bad, and even some of the better ones (like The Player) are a mixed bag. Add to that a difficult genre (war movies) and a hit-or-miss director (Ben Stiller) and you get Tropic Thunder.

While not a complete disaster -- it is genuinely interesting and laugh-out-loud funny in places -- it fails to fire on all cylinders. The one part of the movie that works extremely well is the Kirk Lazarus character, played to near-perfection by Robert Downey, Jr. All of his lines are hysterical and/or insightful, like a mini-manifesto on the rules of Hollywood acting.

If only the rest of the movie were as well-written. The premise is fine: a grizzled veteran (Nick Nolte) tells the titular story of a daring Vietnam rescue, and Hollywood wants to adapt it into a movie. The newbie director (Steve Coogan) is unable to coax convincing performances out of his pampered cast, so the two conspire to stick the actors in an isolated jungle area and shoot the film guerilla style, with cameras in the trees. Soon the actors find themselves without resources or direction, and try to re-enact the story as they find themselves in real-life peril.

But the execution is problematic. A surprisingly muscular Ben Stiller plays the lead, an action hero with a recently spotty filmography. I suppose it was a bit of an in-joke for Stiller to play a Tom Cruise-like character and then cast the real deal against type as a bald, obnoxious Hollywood producer, but in the end I don't think either casting choice was that successful. I sort of wonder what might have happened if the two actors switched roles. Could be a lot better, could be a lot worse. I don't know.

But my quibbles there pale in comparison to the movie's biggest liability: Jack Black, who stretches to play a flatulent comedy actor trying something serious for a change. Usually I tolerate his manic shtick in other movies because there's a calming element (like Mos Def in Be Kind Rewind, or the students in School of Rock) that helps restore the equilibrium. But there's none of that here, so he's a major suck of time and patience. I sympathized with the actors (Brandon T. Jackson and Jay Baruchel) who share scenes with him, and hoped his character would just die.

One of the film's unintentional strengths was its ability to make me think a lot about what I would have done differently. Black has to go, obviously. Stiller might work in Black's place. I'm not sure the big-name actor who plays Stiller's agent (I won't spoil) should be in more than one scene, much less be the film's moral center. Maybe a better director needs to be at the helm. There are a lot of pieces to move around; it might make a nice industry parlor game.

If you do plan to go, pay attention as the real previews wind down, because the best stuff starts long before the opening credits.