It was billed as the "unofficial" Met gala after-party, though you wouldn't have known that from the glammed-up crowd that started filing into the Boom Boom Room not long after midnight. Kristen Stewart and Nicole Richie had switched into jeans and leather leggings, but others spent the wee hours trying to track down precious gems and avoid train wrecks. Mickey Rourke snatched a flashlight from a staffer to help Dree Hemingway hunt for an earring Rosie Huntington-Whiteley had lost, and Prabal Gurung came to the rescue of Katie Lee and Monique Péan, making quick alterations to their hemlines.
Blake Lively and Florence Welch squealed and exchanged stories from the night, oblivious to Marc Jacobs and Lorenzo Martone holding hands as they squeezed past. When "Dog Days Are Over" came on full blast, Welch made a break for the dance floor with Stefano Pilati, where the white-clad duo broke into a dance-off. Welch only briefly put the breaks on her hippie goddess moves to greet Tara Subkoff and Karlie Kloss.
In a nearby booth, Kirsten Dunst was immersed in conversation with Sofia Coppola. Before heading to the back of the room with Leonardo DiCaprio, Kanye West paused to chat with Met ball first-timer Amar'e Stoudemire. Surveying the scene, Lively—who'd had Karl Lagerfeld by her side at the gala—reflected on the unexpected way her evening had started out. "Before we came tonight, Karl and I met at a diner where we saw a bunch of 80-year-olds," the actress told Style.com. "We just had tea and took pictures."