Everyone in the cast of "Gossip Girl" is hooking up with each other - and Chace Crawford and Taylor Momsen are at the center of the latest smooching session. A Page Six spy spotted the co-stars sneak away during their holiday party at Haven on East 51st Street to steal kisses in the corner, but Crawford's rep denies it. We reported last week Ed Westwick and Jessica Szohr were kissing in an airport, and original "GG" couple Blake Lively and Penn Badgley are still going strong. [P6]

Quickly! Someone check Chase's fake/real Facebook page and see if he's posted any "in a relationship" indicators! Also, poor Blair Waldorf/Leighton Meester: she is the odd member out in the cast of incestuous canoodling. One wonders if its part of the contract that Josh Schwartz made his cast sign that they can only make out with one another, or if he just slips them doses of ecstasy during their holiday parties and invites Page Six to watch the orgy.