Get ready for “Tropic Thunder” one of the funniest films to come out of Hollywood in some time. Chocked full of unexpected twists, turns and characters, the film almost makes you forget a risky move made by the filmmakers. But in a film filled with risky moves, a white man playing a black character seems to be secondary. What potentially could be a somewhat controversial film is actually a laugh riot. Robert Downey Jr. (“Iron Man”) stars as a black man, and in the context of the film, he pulls it off.