1 / 33 Joseph Gordon-Levitt

<strong>Age he started:</strong> Age 7 (1988) <strong>Then:</strong> He got his first major TV role on ABC's 1991 "Dark Shadows" series before starring on NBC's short-lived "The Powers That Be." Then, of course, was his stint on "Roseanne" before landing a lead on "3rd Rock From the Sun," which lasted six seasons and launched his career. <strong>Now:</strong> JGL is a major movie star, headlining hits like "(500) Days of Summer," "Inception," "Looper" and "The Dark Knight Rises."

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