9. Robert Downey Jr. Was Trained To Play Tennis & The Violin Left-Handed - Chaplin
Similarly, Robert Downey Jr. earned a Best Actor Oscar nomination for his sublime turn as Charlie Chaplin in Richard Attenborough's 1992 biopic Chaplin, and went to considerable lengths to capture the essence of the Hollywood icon.
Downey worked with a coach to imitate Chaplin's posture and the general way with which he carried himself, and was also taught to play the violin and play tennis left-handed like Chaplin, being naturally right-handed himself.
Given that the actor is only seen playing left-handed tennis for a few seconds of the final film, however, that's quite the amount of (arguably unnecessary) effort.
Nevertheless, those few left-handed tennis serves do at least seem completely believable, and Downey ended up Oscar-nominated all the same, so who's to knock him?