John Wayne as Genghis Khan in The Conqueror (1956)

John Wayne's casting as Genghis Khan is widely regarded as the most egregious miscasting in Golden Age Hollywood, as the actor delivered his signature American drawl while portraying a Mongol emperor. The film's legacy is further tarnished by a tragic footnote: it was shot 137 miles downwind of a nuclear test site in Utah, and of the 220 cast and crew members, 91 developed cancer over the following decades—a cancer rate 3x that of the general population. This catastrophic combination of cultural insensitivity and real-world tragedy gives the film a historical notoriety that far surpasses even the controversial casting of Mickey Rooney in Breakfast at Tiffany's.