Joseph Gordon-Levitt is one of Hollywood's hottest guys, but he wasn't always this way. Back in the '90s, when he started his career as an alien on 3rd Rock From the Sun, no one would have guessed that he would later transform into one of the most swoon-worthy celebs ever. Through the years, JGL has donned many looks for roles and in real life, including a bulked-up New Jersey sex addict and a goofy-faced lip-syncer, and we're rounding them all up below. We'll just forget that he has a girlfriend for now . . .