<Tr> <Td_colspan="2"> List of Gossip Girl episodes </Td> </Tr> <P> "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 . </P> <P> "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 . </P> <P> To prove she is able to handle her own affairs, Serena refuses to leave jail with either Lily or CeCe (Caroline Lagerfelt) although Lily drops the charges on which she had Serena arrested . Rufus (Matthew Settle) is also angry with Lily for Serena's arrest; Dan (Penn Badgley) and Jenny (Taylor Momsen) inform Vanessa (Jessica Szohr) that Rufus returned home without proposing to Lily, and he has remained in his bedroom ever since . Lily feuds with CeCe for telling Rufus about their lovechild . From jail, Serena encourages Blair (Leighton Meester) to enjoy prom with Nate (Chace Crawford) in the way Blair had chronicled in a scrapbook as a preteen, but each of the couple's prom plans, such as the limo, hotel reservation and Blair's dress, inexplicably go awry . Nate suspects Chuck (Ed Westwick) of sabotaging the prom in an effort to win Blair back, but Chuck denies involvement . Dan convinces Serena to allow him to pay her bail and escort her to the Prom . </P>

Who plays lily's mom on gossip girl