Advocacy groups have urged a boycott of "Tropic Thunder" because of the repeated use of the word "retard, " when Mr. Downey's character gives Tugg an acting tutorial.

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His summer was capped off by his Oscar-nominated work in Tropic Thunder playing a white actor playing a black actor in a war movie.

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But, he said, "Tropic Thunder" is a long way from the days when white performers would don blackface as a way of exploiting black stereotypes.

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In "Tropic Thunder, " a comedy about self-absorbed Hollywood types making a "Platoon"-style war movie, Downey plays Australian actor Kirk Lazarus, a multiple Oscar-winning performer who gets so involved in his roles that he forgets to come out of them.

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Cruise made a similar move in the 2008 movie Tropic Thunder.

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"Tropic Thunder, " which was co-written and directed by Mr. Stiller, is like a dinner whose hors d'oeuvres are far more satisfying and well-composed than the slightly warmed-over main course.

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