Watch out, Upper Eastsiders. One-time tween sensation Hilary Duff has joined the cast of The CW's Gossip Girl, to appear in a multi-episode arc. Entertainment Weekly reports Duff will play Olivia Burke, "a movie star who enrolls at NYU in search of a traditional college experience," not unlike a few other recent NYU students we can think of. Her character will room with Vanessa Abrams, played by Jessica Szohr, promising drama galore. The actress/singer/designer will debut in this season's fourth episode, slated to air the first week of October.