Robert Downey, Jr. and Jay Baruchel (FANBOYS) have signed on to star in the upcoming Ben Stiller comedy TROPIC THUNDER for DreamWorks. Downey, Jr. will actually star in the role Stiller had been recruiting Tom Cruise for, playing Kirk Lazarus, “the greatest actor of his generation.” In the film, Downey, Jr. and Baruchel will play actors shooting a war movie where they mistakenly get caught up in a real war-like situation. Stiller is directing the film from a script by Justin Theroux and Etan Cohen. Theroux and Stiller are also expected to star in the film. Downey, Jr. will start working on THUNDER this July after he wraps work on Jon Favreau’s IRON MAN. He can be seen in David Fincher’s ZODIAC this Friday. Baruchel can be seen this summer in Judd Apatow’s KNOCKED UP.