From scaling the steps of the Met to hobnobbing with celebs of every stripe to the inspired performance by Lady Gaga, you would think that the gussied up guests of last night's Costume Institute Gala would have been too exhausted to charge on. But alas, the fashion pack is nothing if not resilient so the festivities continued way into the early morn at an impromptu fete held at the 18th floor of The Standard Hotel. (Perhaps everyone was inspired by La Gaga's ra-ra-ra-ra-rah roar as she ended her stage act with "Bad Romance.")

At 1am it started out as a relatively calm affair, except if you noticed that oh, there are adorable twentysomethings/designers Alexander Wang and Joseph Altuzarra dancing in the corner. And yes, that cute tan girl flitting about in a long T-shirt, sparkly skirt, and Converse sneakers does happen to be Blake Lively. And hey now, isn't that Ben Stiller, talking to Malin Akerman, talking to Ed Norton, who just arrived with Liv Tyler?

Perhaps the brightest star of the bunch was none other Katy Perry who literally illuminated the dark room in her dress lined with LED lights. And even though the frock's on/off switch (a.k.a. her "panic button") was tucked into her bra, she still encouraged curious bystanders to give it a flick. "She literally stuck my hand, like, in her boobs," said a bemused Elettra Wiedemann.

Well into the wee hours, Perry's fun-loving antics didn't stop. She also crawled across the floor to stick her head under Kristen Bell's DVF dress while the nonplussed actress shook her head and continued to peck away on her Blackberry. Energized by the mix of Gaga, Rolling Stones, and Madonna playing courtesy of the Misshapes, Perry then took to dancing atop of the bar's piano lit up like a firefly.

Also in the dancing mood was Chloe Sevigny, who cut some serious rug to the Pet Shop Boys' "West End Girls" with her dress designers Jack McCollough and Lazaro Hernandez of Proenza Schouler. Nearby a cute couple in the form of Sienna Miller and Jude Law canoodled at the bar.

And in case the wall-to-wall celebs, blaring music, and full Champagne glasses weren't enough of an indicator of a hooting hollering good time, there was always the aftermath. Ripped shirts, kicked off shoes, and in DJ/model/fashion star Leigh Lezark's case, plumage. Her black feathered Christian Siriano frock molted all over the chic bar.

"Did someone sacrifice a crow?," one party-goer wondered aloud as he stumbled out.