Paris Hilton’s birthday may have sucked, but the guest of honor sure had a hot topic of conversation to keep them snickering-a recently bald Britney Spears.

Brit’s been avoiding former party girl buddies like Lindsay Lohan and Paris Hilton:

“Britney was the butt of everyone’s joke. All the girls kept saying how fugly she looked as a baldie,” one Hilton pal giggled.

Britney further proved that she has officially been removed from the A-List when the Toxic singer crashed a stranger’s party, only to be left sitting alone in a black leather booth.

Sporting a bargain basement cheap blond wig, embarked on a sad party crawl, her constant entourage – hired help including bodyguards and backup dancers -were M.I.A.

The usual glamorous preparty was replaced with a low-key early bird dinner, with the only man still by her side, dad Jamie, at the rowdy New Orleans-themed Stevie’s Creole Cafe in Encino, Calif. The family summit took place over $10 cups of gumbo.

“Britney and her dad ate in a private VIP section,” says a restaurant staffer. “She was wearing a blond wig and a black hat. She was in such an intense conversation with her dad that no one wanted to bother her.”

Britney would reprise her meal seven hours and 19 miles later at the Rainbow Bar & Grill in West Hollywood, where she sneaked in for another bite.

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

The staff of the club, where the late comedian John Belushi spent his final hours, didn’t notice the wigged-out star’s arrival – and never even offered her a drink. “She spent most of her time sitting alone in a booth,” said the stunned staffer.

One party guest, caught up in the karaoke, requested Spears’ “… Baby One More Time,” unaware Spears was in the building.

The crestfallen crooner left around 1 a.m. with a brunette friend, who drove her in a sedan. The two made one more stop, dropping by the upscale Beverly Hills Hotel, where paparazzi following the car had to be removed from the driveway.

Reps for the hotel refused to comment on whether Britney stayed for cocktails in the Polo Lounge or checked in for the night.