In case your Instagram, Twitter, and Snapchat accounts are simultaneously out of order, the international fashion pack came together in New York last night to celebrate the launch of Balmain x H&M. Even the presence of guests like Diane Kruger, Rosie Huntington-Whiteley, and Kylie Jenner in the front row—and the stomps of models Jourdan Dunn, Joan Smalls , and Gigi Hadid on the runway— couldn’t overshadow the main event. In the span of one evening, Olivier Rousteing transformed a downtown locale with a crew of voguers, a packed pop-up shop, and the rumor—and ultimate reality—that the Backstreet Boys would reunite for a special performance. (Rousteing did promise a once-in-a-lifetime experience, after all.) This being Balmain, it was all about the details. The seating assignments resembled futuristic plane tickets and the after-show snacks were burgers and fries in branded black boxes. Many a partygoer was decked out in Balmain—and some even tossed their originals aside to try on the H&M offerings. The high point of the evening was no doubt the return of the Backstreet Boys, who pleased the A-list crowd with hits like “I Want It That Way” and, natch, “Everybody (Backstreet’s Back).” The music was the same, the dancing even better, and the fashion—Balmain for H&M, of course—was a clear improvement over the group’s ‘90s getups. “Thank you Olivier!” the Boys shouted as they exited the stage. Thank you Olivier, indeed.