A cast of actors shooting a gritty war movie winds up in the middle of a real conflict ...with real bullets ...in the new action-comedy co-written, directed by and starring Ben Stiller along with Robert Downey Jr., Jack Black and Nick Nolte. Alan Silverman has a look at Tropic Thunder.

It's a movie in trouble. The actors and film crew are in Vietnam, recreating the dramatic wartime experiences chronicled in a best-selling novel titled Tropic Thunder; but making the film turns into a monumental clash of egos.

The flummoxed first-time director is played by English comic actor Steve Coogan.

"There are a lot of directors out there who can tell you how good they are," Coogan notes. "There are very few that are actually good ...really good ...at what they do. The character I'm playing is one of those guys who can intellectualize and deconstruct things and explain the methodology of what he's doing, but when it comes to actually doing it he's out of his depth."

It doesn't help that his cast is a mismatched jumble of performers: Kirk Lazarus, an Oscar-winner from Australia who stays in character whether the cameras are rolling or not; Jeff Portnoy, a corpulent comic who is trying to make the transition from gross-out comedies to genuine drama; a rap star with the stage name 'Alpa Chino' - that's A-l-p-a Chino - who fancies himself a raw talent ready to be discovered; and Tugg Speedman, an action star who is a bit past his prime. Writer and director Ben Stiller takes on the Speedman character.

Ben Stiller in scene from Tropic Thunder

"The whole idea of the movie is really to make fun of actors and how far actors go, self-important actors, actors who want recognition ...making fun of the need that actors have to be taken seriously," Stiller explains.

Perhaps the most outrageous example of that is the Aussie Academy Award-winner Lazarus, played by Robert Downey Jr.

Lazarus has been egregiously miscast as an African-American soldier; but, determined to play the role, he undergoes a medical procedure to darken his lily-white skin. Downey admits that out of the context of the movie it sounds offensive, to say the least; but he says the idea is, in the name of comedy, to lampoon the sort of actor whose massive ego lets him ignore any sense of civility.

Robert Downey Jr., right, and Ben Stiller in scene from Tropic Thunder

"I know from, occasionally, my own experience, but much more often by observation that there is nothing more disgusting and entertaining than watching an actor who is taking himself very seriously," Downey says.  "I thought to couch that in someone putting himself under the impression that he could represent the black experience is so wrong and so creepy. I'm not qualified to discuss this stuff, but I know that as far as my integrity as a man and an artist, I knew that past a certain point it was far more entertaining than controversial."

The only 'normal' person in the cast is newcomer Jay Sandusky, a dedicated young actor played by Canadian Jay Baruchel.

"I knew that I had to be the straight man, just try my best not to step on everyone else's jokes and set them up as well as I could, whilst maybe, possibly being funny myself if I got the chance," Baruchel says. "I just had to be as earnest as I could because I'm the 'cooler head.'"

There are also cameos by Matthew McConnaughey as a fast-talking talent agent and Tom Cruise, barely recognizable in elaborate makeup, as a crude, but powerful, studio boss. Ben Stiller says poking fun at Hollywood may be like the proverbial "biting the hand that feeds you" ...but it's just such a tempting target for satire.

Brandon T. Jackson, left, Ben Stiller, center, and Robert Downey Jr. in scene from Tropic Thunder

"In a movie like this there's a lot of pushing the envelope," notes Stiller. " I'm playing an actor who played a mentally impaired guy to try to win an Oscar. Tom Cruise is playing this foul-mouthed studio executive. It's not underlined, but all this stuff is out there that people could really interpret the wrong way and it felt like that's what this movie is. As long as we're clear about what we think is funny about this and as long as we have our intention in the right place, that's all we can do and let the movie speak for itself in the context of the movie."

Tropic Thunder also features Jack Black as washed-up (and strung-out) comic Jeff Portnoy. Brandon T. Jackson is rapper Alpa Chino. Nick Nolte as the grizzled Vietnam veteran whose memoir is being filmed. Danny McBride plays a trigger-happy special effects expert who just loves blowing things up. The purposely over-the-top musical score is by Theodore Shapiro; and Tropic Thunder was shot on location in the jungles of Maui, Hawaii.