(HOLLYWOOD REPORTER) ? Michelle Trachtenberg (Buffy the Vampire Slayer) is doing a multi-episode arc on the CW series Gossip Girl. She will play Georgina Sparks, a girl who pops into Manhattan after spending time in rehab and shakes up the life of Serena van der Woodsen (Blake Lively). Georgina is a character from the books on which the series is based. The arc will air during May sweeps. Mischa Barton was at one time rumored to be set for the role. Trachtenberg just wrapped the feature Seventeen Again, which also stars Zac Efron. (Hollywood Reporter)