Since the script called for an "overweight gross-out comedian with a drug addiction," who better to cast than Jack Black? The actor has just signed up to play a character named Jeff "Fats" Portnoy in Tropic Thunder, to be directed by Ben Stiller. Written by Justin Theroux (who starred alongside Stiller in Zoolander and Duplex) and Etan Cohen, pic follows a group of actors who run into a whole mess of trouble while filming a big-budget war movie, forcing them to become the commandos they are playing. Think of it as Three Amigos! meets another wacky Ben Stiller comedy.

Along with Black, Robert Downey Jr. will play four-time Oscar winner Kirk Lazarus, known as the "greatest actor of his generation." Jay Baruchel will tackle an unknown actor named Kevin Sandusky and Stiller plays a dude named Speedman -- who, I assume, will be all amped up and ready to kick major ass (ie: typical Stiller shtick). Theroux also stars, though there's no word on who he is playing (maybe the washed-up actor looking for a second chance?). It's funny that Black should land this part, as his character's major obstacle is that he must give up a drug addiction in order to shoot in the jungle. Sound familiar? Back when Black was on a brief hiatus from filming King Kong, the guy took the opportunity to get absolutely sloshed, partying it up as if there were no tomorrow. I guess those jungles really get to a guy, huh? Tropic Thunder is currently scheduled to hit theaters on July 11, 2008.