(November 11, 2011 - Source: Mike Coppola/Getty Images North America) more pics like this »
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11. Michael J. Fox in 'Back to the Future: Part 3'

Michael J. Fox was 24 when he started playing 17-year-old Marty McFly in the first Back to the Future movie. But since all three movies take place within a few months of each other, the actor was 29 and still playing 17 when the third movie was released.