How do you follow up a mega-party featuring a performance by Amy Winehouse? If you're Karl Lagerfeld—and you're looking to top the Winehouse-fueled spectacular you orchestrated for Fendi last year—you tap another of fashion's musical darlings and let her loose. Beth Ditto, the Kaiser's on-trend pick for the Italian company's Wednesday-night blowout, didn't disappoint. Performing with her band the Gossip, Ditto inspired mosh-pit levels of excitement in a room packed with exhausted showgoers. "I was so tired today," Julia Restoin-Roitfeld said from her perch on a banquette at the VIP Room Theater in Paris. "I call it fashion week fatigue. But this? This is amazing."

Ditto took to the stage after midnight, which, while later than advertised, didn't bother guests like Kate Moss, Jamie Hince, or Angela Lindvall—perhaps no surprise there. Fresh-faced and shimmery in a sequined cocktail dress, Ditto treated fans to her trademark energetic screaming, flailing, and rolling around. When she had a little trouble removing her sequined boy shorts—stripping being one of the singer's signature stage moves—she asked Ellen von Unwerth to hold her mic while she got them off. At one point, Ditto even brought the youngest member present from the Fendi clan onstage for a little swing dancing. "I love you, Beth," Moss screamed from a balcony. The frenzy ended when the singer collapsed in a sweaty heap on the illuminated floor wearing nothing but her intimates and a destroyed fishnet body stocking.

Lagerfeld, for one, was thoroughly entertained. "So much energy," he said just after the performance. "And her voice isn't bad. Lucian Freud should paint her." Good idea, though there are doubts she could stay still long enough for a portrait.

— Derek Blasberg