Of course we always enjoy seeing celebrities abandon their red carpet personas and let loose, but when they start emerging from nightclubs barely standing and sporting lipstick marks on their collarbone, we start to worry. After obediently posing for pictures at last night's premiere of Leatherheads in London, Renee Zellweger dove bob first into the party scene alongside a better-behaved George Clooney. And, as these pictures show, Zellweger may have downed one too many pricey cocktails across the pond.