Britney Spears crashes a stranger's party !

Troubled pop tart Britney Spears crashed a stranger's party on Sunday night.

Wearing a cheap blond wig, Britney Spears crashed a party at Roxy, a classic L.A. music hot spot.

"It was a private party," says a club spokesperson. "There were 80 people there."

"She spent most of her time sitting alone in a booth," said a worker

One party guest, caught up in the karaoke, requested Spears' "... Baby One More Time.

Spears then went to the Beverly Hills Hotel, where paparazzi following the car had to be removed from the driveway reports Page Six.

Since shaving her head on Friday, Spears has avoided former party pals like Lindsay Lohan and Paris Hilton. Spears' previous posse cavorted in Las Vegas over the weekend at Hilton's 26th-birthday bash, where the singer was a hot topic of conversation.

"Britney was the butt of everyone's joke. All the girls kept saying how fugly she looked as a baldie," one Hilton pal says

In other news, Britney Spear's ex, Kevin Federline canceled plans to party in Las Vegas during NBA All-Star weekend, to offer support to troubled Britney Spears and their sons, Sean Preston and Jayden James reports PR-Insider.

A source told People magazine: 'Kevin is concerned for Britney and his children. He loves her. He's always loved her - even after she started divorce proceedings.' The 28-year-old had booked a room from February 14 - 19 at Las Vegas' Venetian Resort Hotel Casino, but canceled the reservation.