Kirk Lazarus in Tropic Thunder
The casting of Robert Downey Jr. as a white actor who plays an African-American man in a film by wearing blackface was a hot topic for months after its release. Downey defends the decision to this day, claiming that the controversial choice was meant to be ironic.
Mystique in X-Men: First Class
Jennifer Lawrence endured hours in the makeup chair for this role. In the comics, Mystique had many costumes, including a famous white dress with a slit up the side. In the movie, the costume designers decided that the character should forego clothing entirely.. She is a mutant, after all.