What a roller coaster day in Paris. While French newspapers reported the end of the house of Lacroix as we know it, 2,500 members of the fashion elite enjoyed an evening of cotton candy and champagne at the Grand Palais, where Sonia Rykiel and H&M pulled out all the stops to celebrate their mostly-undies collaboration (in stores December 5). Etienne Russo, the master showman from Belgium responsible for Paris’s most over-the-top extravaganzas, including Chanel’s Marie Antoinette roll in the hay last October (also at the Grand Palais), pulled in a 30-meter-tall Eiffel Tower decorated with 25 kilometers of Christmas lights, as well as a Ferris wheel, a six-meter-high inflatable chocolate poodle and other amusement-park attractions. A corridor lit by neon Sonia-style stripes led to a smoky purple and pink lit enchanted forest filled with balloon trees and giant white rabbits. Wait, was that champagne we were drinking?

Guests mingled in a life-size Disney-esque take on gai Paree, complete with the Arc de Triomphe, Left Bank cafés and a Sonia Rykiel for H&M shop, which was the busiest stand of the evening, with all sales going to Unicef. Guests were dressed tartly in fake leopard furs, droopy bows and plenty of glitter as they downed sandwiches and coupes before the promised parade. The celebrity roster was heavy on French actresses: Emmanuelle Beart, Ludivine Sagnier and Elodie Bouchez, with Kate Bosworth heading the Anglo contingent, along with Alice Dellal, while Haider Ackermann, Loulou de la Falaise and Jean-Paul Gaultier kept Sonia and her daughter Nathalie Rykiel in good fashion company.

The parade was simply gobsmacking. Beginning with the Arc de Triomphe, which split in two amid an explosion of fireworks, Rykiel’s girls strutted their stuff on giant Thanksgiving-like floats outfitted in negligees, bras and retro undies for H&M. Girls on swings, hanging off chandeliers, on satin beds and bicycles showed all the things you can do to a when you’ve got almost nothing on and you’re listening to a souped-up Abba soundtrack. The pièce de résistance was Lily Cole, her flaming mane a nod to Sonia’s own, perched like a Valkyrie vixen on a huge horse’s head in a black satin bra and panties. And, as if once wasn’t enough, as soon as the parade was over it turned around for an encore. When it comes to a celebration, Sonia never disappoints.

courtesy H&M