For Ashlee Simpson-Wentz, a celebration just isn't a celebration unless it has a catchy theme. When the about-to-pop starlet wed Pete Wentz in May, the inspiration for their shotgun nuptials was Alice in Wonderland. And at her 24th birthday party on Oct. 3, it was all about class, or lack thereof. "It had a white-trash theme," a guest tells People of the costume party. "Ashlee wore Daisy Dukes and platform flip-flops with a bathing suit and a fake tattoo around her belly." Big sister Jessica opted for "a crazy leopard-print dress that showed off a lot of cleavage," adds the snitch, who failed to explain how, exactly, that frock differed in any significant way from the countrified starlet's usual boob-highlighting wardrobe selections. As for dad Joe, he traded in his blond guylights for a mullet wig, which he paired with -- scary visual place, people -- a cut-off muscle T-shirt, according to the mag. Munchies included corn dogs, mac and cheese, chicken fingers and French fries, because apparently Spam- and roadkill-related menu items would have been offensive.

Mariah and Nick celebrate his birthday in Las Vegas on Oct. 7.

In other birthday news, Mariah Carey tossed a bash for surprisingly enduring husband Nick Cannon's big 2-8 in Las Vegas on Tuesday night. Unfortunately, he didn't get the evening off to mix and mingle. People reports that the actor worked the DJ table during the shindig at hot spot Pure as his high-maintenance half chitchatted with guests and sipped wine at a nearby VIP table. After a towering cake was served, Cannon took to the microphone to tell Carey, "Thank you, my love." Chances are he was equally grateful over another recent gig. Mariah tapped him to direct her latest music video, "I Stay in Love," which was shot during their Sin City stay.

Zac keeps his hair in check at the London premiere of "High School Musical 3" on Oct. 7.

Some people simply don't appreciate the hard work that goes into being a teen idol. The London Daily Mail says the perfectly coiffed golden locks that delicately swoop over Zac Efron's zit-free forehead came dangerously close to being mussed after he had a creepily close encounter with a middle-aged fan. Seems the pretty boy, 20, and girlfriend Vanessa Hudgens, who are globe-trotting to promote "High School Musical 3: Senior Year," were exiting the Josh Hartnett-starring London stage production of "Rain Man" on Wednesday night when the demographically challenged fellow made a grab for Zac's well-tended tresses while hurling a few choice words his way. "Some guy just stood near the door where Zac and Vanessa emerged," an eyewitness tells the paper. "He just reached over and grabbed the side of Zac's head. There was no provocation. It all turned into a bit of a mess. He was shouting all kinds of things at Zac. Their security team eventually dealt with it."

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