Although he plays an A-list movie star on Entourage, Grenier needed this TV role to become a bona fide celebrity. In the late '90s, his quirky persona, Groucho Marx eyebrows and perpetual five o'clock shadow were featured in a number of films (The Adventures of Sebastian Cole, Drive Me Crazy), but Entourage proved that this scruffy actor could clean up quite nicely, and be compelling to boot. Off-camera, Grenier is delightfully offbeat. He plays percussion in the "Appalachian glamrock" outfit the Honey Brothers and directed the documentary A Shot in the Dark about his real-life search for his estranged father.