After dinner, the party posse headed off to the Hollywood club Hyde, where Brit met up with BFF Paris Hilton and Fergie.
It seems Britney decided 25 will be a more graceful year; as Spears exited her car, she made sure to hold her knees together in order to avoid any more embarrassing tabloid shots.
But before Brit got wild on Saturday night, she started her weekend with a trip to the zoo with her son, Sean Preston.
Although the candles burned out on their marriage, "Extra" spied Kevin Federline in Malibu over the weekend, where he reportedly dropped by to wish his former pop princess a happy birthday.
Meanwhile, just a week after announcing his breakup from Pam Anderson, Kid Rock wasted no time getting reacquainted with the single life this weekend.
"Extra" spotted Kid out in Sin City, surrounded by a gaggle of women. He even kissed one blonde while another hugged him around his neck.
Over on the East Coast, Cover Girl Christie Brinkley and her philandering ex came face to face in the Hamptons.
Christie, who was surrounded by her kids, accepted an honor at her son's school.
And for the very first time, the cheating ex, Peter Cook, is opening up to People magazine about life after Christie.
"He talked about the fact that he's been going through a really tough time," People's Galina Espinoza said.
As Peter dwelled on the past, Jenny McCarthy looked ahead with her main squeeze, Jim Carrey.
McCarthy served up the real dish about her relationship with the funnyman to "Extra," with whom she went very public with at Tom Cruise and Katie Holmes' wedding.
"We're both not planning it at all," she said. "We're very happy where we are, and that's it."