Tinsley Mortimer and Fabiola Beracasa looked less than delighted at the Y-3 show last night. In a scene straight out of “Mean Girls,” the socialites couldn’t hide grimaces when photographers clamored for them to embrace up-and-comer Olivia Palermo. Reluctantly posing, the pair and Palermo exchanged not a glance. The scene only added to the show’s sophomoric ambience: the Hunter College gymnasium.

Indeed, Y-3 drew an assortment of cliques: The hip-hop crew was Russell Simmons and his brother the Reverend Run; Leelee Sobieski and beau were the popular kids; Fischerspooner’s Casey Spooner stood up for the art punks; French headbutter/footballer Zinedine Zidane was the jock contingent. Oh, and Cuba Gooding Jr.? He’s the kid who’s always hanging around but no one knows why.

* Spirits were decidedly warmer at Gotham Hall, where Adrien Grenier and Piper Perabo were all smiles for G-Star. Even the Misshapes politely explained that they just didn’t do grins.

* But the sweetest? That would be Tommy Hilfiger and family. Rapper Junior’s hip-hop cred was apparent by his ginormous medallion of Richie Rich – the comic-book character, not the clothier. Also by the fact that squeeze Dee Ocleppo had to explain to him who the Misshapes were.

* The hottest accessory at fashion week? An assistant. Too bad it’s so hard to find a place to put one. The other Michelle Williams – not Heath Ledger’s baby Mama – had a devil of a time placing hers at Vivienne Tam last night. Seems the man sitting directly behind her wouldn’t cede the seat. Same thing happened at Heatherette Tuesday night when a colleague was asked to accommodate Kimberly Stewart’s personal slave. Nothing doing.

* Which small-screen star was so unhappy with her outfit for the Red Dress show that at the last minute, she asked the designer to cut the dress into a more revealing shape so she could show off her best assets?