Thank goodness for Sonia Rykiel. The Paris legend resuscitated what was becoming a bleak season (blame the markets) with a 40th-anniversary dinner-and-show party that goes down in this reporter's notebook as the most spontaneously exuberant and genuinely fun fashion event in recent history. After a long trek to Saint Cloud and an even longer wait for the entrée, it felt like the night was going to turn into a chore. But by the time three models vamped their way down the elevated runway in metallic silver-and-black striped sweaters and skirts (specifically, that would be somewhere between the opening run of house-signature candy-colored tops and the pearl-embroidered oversize suits and motorcycle jackets), any lingering resentment about the late 11 p.m. start had evaporated.

During the evening-gown section—long tanks and feathery halters and tiers ruffled to the floor—the guests at Olivier Theyskens' table started tossing roses from the centerpiece at the models. (Other luminaries on hand included Jean Paul Gaultier, Zoe Cassavetes, Emma Watson, and Dita Von Teese.) Soon the runway was covered in flowers the color of Rykiel's dresses. Even that couldn't stop the girls from breaking into a dance party when they came out again in taffeta minidresses. A few even conga-lined it straight into the audience.

If that had been it, the audience would've left content. But after taking her bow alongside her mother, Sonia's daughter Nathalie grabbed the microphone and announced, "A birthday without a surprise isn't a birthday. You've been inspiring the world of fashion for 40 years; here's your present. Bon anniversaire, Maman." Out came 30 more models in Sonia Rykiel looks designed by some of fashion's biggest names. Martin Margiela made a fur chubby the color of Rykiel's flame-red mane. Rodarte's sweater dress read "Obama." Jean Paul Gaultier's came attached to giant knitting needles and trailing a ball of yarn. Happy returns, indeed.