5. Jake Gyllenhaal
When your father is a director, your mother is a producer/screenwriter, your older sister is an actress, and your godmother is Jamie Lee Curtis, you're probably going to start your career in the entertainment industry at a pretty young age. Born in 1980, Jake Gyllenhaal made his debut at 11, starring as Billy Crystal's son in City Slickers. He also appeared in a handful of other films and television shows, such as A Dangerous Woman and Homicide: Life on the Streets, before his eighteenth birthday. At the age of 21, his career shot into the stratosphere with his performance as the enigmatic Donnie Darko in the beloved cult classic by Richard Kelly. Since then, he's divided his time between smaller indie projects and high-profile blockbusters, ensuring his continued presence on the big screen.