The "Genie in a Bottle" songstress turned 28 yesterday, and celebrated the milestone with a bash at Los Angeles restaurant Osteria Mozza with famous pals such as Paris Hilton, Nicole Richie, Joel Madden and Benji Madden. (Also in attendance: music-marketing executive hubby Jordan Bratman, 31. )

Aguilera spiced up the affair by dressing up as one of the thuggish droogs from the 1971 Stanley Kubrick classic A Clockwork Orange, as did many of her guests. And given Hilton and Benji Madden's recent romantic split, it's only thanks to the happy holiday spirit that a brawl reminiscent of the movie didn't break out.

Way to keep your soiree interesting, Christina. And it's nice to see that little miss "Back to Basics" is capable of looking to something other than Lady GaGa for inspiration.