On a brisk April day in Long Island City, N.Y., the cast and crew of Gossip Girl are in the midst of filming at the hipster coffee shop Communitea. Dan (Penn Badgley) and gal pal/barista Vanessa (Jessica Szohr) are chatting it up at the counter with new girl Sarah, and offering her tips on navigating the Big Apple. What they don't know is that ''Sarah'' is actually Georgina Sparks (played by doe-eyed Buffy vet Michelle Trachtenberg), a notorious NYC party girl and a former friend of Dan's girlfriend Serena who will use any means necessary to worm her way back into her old BFF's life. Upper East Side-bred Georgina's hobbies include blackmailing, stealing boyfriends, and drugging friends. A few other telling details about Ms. Sparks: As a teen, she sold her riding pony for cocaine. She de-virginized bad boy Chuck Bass (Ed Westwick) when he was in the sixth grade. Oh, and she knows why her best frenemy Serena van der Woodsen (Blake Lively) really fled the city for boarding school a year ago.
It's a juicy role for Trachtenberg, previously known as Buffy's little sister Dawn on Buffy the Vampire Slayer, and she's clearly relishing Georgina's eyebrow-arching villainy. ''It's awesome playing the bad girl,'' says Trachtenberg, who took on the role after The O.C.'s Mischa Barton passed. ''Dawn was a lovely nerd and Georgina is a bitch. There's no way around it. It's in every fiber of her being. It's so much fun to know that Georgina can kill you with a glance.''
Bringing in Georgina is one of a number of twists the producers are pulling out in a bid to move the show from cult fave to mainstream hit. They're amping up the drama, the stakes, and, they hope, the buzz ultimately the most important card the trashy, flashy, and fun series holds. In an era where the teen girl has become Hollywood's most lucrative power demo (see: High School Musical; The Hills), Gossip Girl has emerged as something unique during the underwhelming 2007-08 television season: a show people actually talk about. To help build anticipation before the show's April 21 return, The CW launched an aggressively sexy ad campaign, complete with controversial posters emblazoned with ''OMFG'' (a slightly raunchier take on the text-message standard ''OMG'').NEXT PAGE: ''We're not looking to inject artificial levels of melodrama to boost ratings,'' says executive producer Josh Schwartz