The demise of 'Melrose Place' last season may prove to be good news for 'Gossip Girl.' The CW series has signed 'MP' star Katie Cassidy for a multi-episode arc, in which she will play a trouble-making Columbia student who becomes a love interest for Nate (Chace Crawford), according to the Ausiello Files.

However, Ausiello's source indicates that Cassidy's character "is not what she appears," which on the Upper East Side can mean anything. (Maybe the CW is looking to inject some of that 'Vampire Diaries' ratings love into 'Gossip Girl,' and she's a vampire. Or a ghost, like on 'Grey's Anatomy.'?)

Okay, none of those things are probably true, but as one of the few watchable characters on 'Melrose,' Cassidy should help bring a new energy to 'GG''s fourth season.

'Gossip Girl' saw its ratings slip in its third season, averaging only 2 million viewers. Cassidy joins 'Harry Potter' actress Clemence Poesy as new blood for the new season, hoping to reinvigorate the flagship series.

Meanwhile, Cassidy, the daughter of actor David Cassidy, remains active in the film world: She just wrapped the new film 'Monte Carlo' with fellow 'Gossip Girl' cohort Leighton Meester.