Yeah, the movie is about actors making a war movie in a jungle in Asia and accidentally getting mixed up in a real conflict.

RDJ plays a white, blond, blue-eyed, Australian method actor who was cast as a black character. As a method actor, he stays in character the entire duration of the shoot, so he’s always in blackface, acting as his character. Early in the movie there’s a montage of his other roles, so the audience and all the characters are fully aware that he’s a white Australian in blackface going overboard with his method acting.