Robert Downey Jr. dons "blackface" in a hilarious and potentially controversial role this summer in 'Tropic Thunder,' invading theaters Aug. 13, and ET has a first look at the 'Iron Man' star's on-set make-up transformation!

Downey Jr. plays opposite Ben Stiller and Jack Black as Kirk Lazarus, a four-time Oscar winner and "greatest actor of his generation" who finds himself in the middle of actual combat when everything that could possibly go wrong goes wrong on his big-budget war movie.

Watch ET tonight for more!