"Valley Girls" is the twenty-fourth episode of the second season of The CW television series Gossip Girl. The episode served as a backdoor pilot for a potential Gossip Girl spin-off series set in the 1980s, entitled Valley Girls. The episode was directed by Mark Piznarski and written by Josh Schwartz and Stephanie Savage (this was the first episode of the series since "Much 'I Do' About Nothing" to be co-written by Schwartz). It was filmed on location in New York City, New York and in Los Angeles, California. References to elements of 1980s popular culture were heavily accentuated in the episode, which the producers hoped would bridge the generation gap between the characters and audience. "Valley Girls" aired on the CW in the United States on May 11, 2009 and was viewed live by an audience of 2.31 million Americans. Although the episode received generally positive reviews, the spin-off series was not picked up.

"Valley Girls" provides insight on the mysterious past of character Lily van der Woodsen (played by Kelly Rutherford as an adult and Brittany Snow as a teenager) through a series of flashbacks to her life as a teenager in the 1980s. In the past, Lily runs away from her wealthy parents to live in the San Fernando Valley with her sister Carol Rhodes (Krysten Ritter), the black sheep of the family. In the present, Lily's daughter Serena van der Woodsen (Blake Lively) rebels against her mother while her classmates prepare for the Prom. The episode introduces the main cast of Valley Girls as guest actors.

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