With elbow space and oxygen in short supply (but booze flowing for miles) at the jam-packed Marc Jacobs after-party Monday night, everybody’s celebrity radars went on overdrive - with some woefully inaccurate results.

"Dude," a guy whispered, pointing to us - yes, us - as we sidestepped past him and his friend with difficulty. "She was totally on Leno the other night, but with a way different hair color."

It’s understandable that the lads were having a tough time of it. The party at the Gramercy Park Hotel was teeming with socialite life - check out the pics - plus plebes like us just trying to move around without getting bruised.

Successfully spotting familiar faces through the mob was an uphill battle; we didn’t even get a drink - sacrilege! - because the crush of high-heeled humanity at the bar dwarfed our patience.

Lil’ Kim had it right - she beelined for a booth in the back corner, where a few burly guards kept watch, perhaps making sure nothing fell out of her off-the-shoulder brown velvet dress. Doing lap after slow lap, we brushed past a rather haggard-looking Dylan McDermott; bumped arms with a cranky (and, we suspect, departing) Victoria Beckham in a strapless white tutu dress that brought back our worst ninth-grade dance memories; made way for lean and spiky movie producer Brian Grazer and his statuesque date, who were being led through the crowd by a particularly pushy handler; bypassed supermodel Helena Christensen, who changed from the safety-pinned cotton print dress she wore to the show into a plain black sheath; and got a good look at Mischa Barton by the bar. From all the way across the Armory at the show itself, Barton’s spangly silver balloon of an outfit looked like the love child of a disco ball and choir robes, but it did at least gleam as if expensive. But somebody should get sued if it actually was. Up close, the thing resembled a gray sweatshirt with sequins glued onto it, and it ate her slim body whole.

As such, it was probably one of the best-fed things in the room - certainly better than Kate Bosworth, who is just as naturally pretty as Barton but was letting it all hang out (and by "all," we mean "her well-defined sternum bones") in a white linen-looking dress that dangled loosely around her controversially slender frame. Her date was a tall, male-model sort who was getting sucked into the drama of a pouting Julia Restoin-Roitfeld, who flounced around in a tarty, gold faux-lace number and appeared to be in a righteous huff.

Winona Ryder, one of the models in Marc Jacobs’s series of nude posters dedicated to skin-cancer awareness, got swarmed by photographers - and one horny partygoer in a white and black plaid coat, whose friends whooped that he was "goin’ for it." As she posed with Jacobs under a black-and-white framed version of her poster, she could barely take two steps before a newly arrived cameraman begged to steal a few more seconds of her time. Her suitor in the jacket turned and skulked away, defeated. Perhaps he settled for her in T-shirt form: For a $20 donation to a charity benefiting skin-cancer research, partygoers walked away with their choice of the eleven portraits emblazoned on a tee, plus a gift bag containing a large bottle of Marc Jacobs perfume, some sunscreen, and a 30 Seconds To Mars CD, which explained the presence of lead singer-actor Jared Leto.

And then there was the eavesdropping. As we lurched toward a raven-haired Michelle Trachtenberg, we heard the following dishy conversation snippets: "I mean, I was flattered, but I would never do it," she said. Fifteen seconds later, "Not my boobs. Just my ass."

Now there’s something we’d like to see on a T-shirt.

 The Fug Girls