"I can barely speak English, what do I need to sing for?" asked Calvin Klein's Francisco Costa, nimbly sidestepping his turn at karaoke during the Whitney Contemporaries annual Art Party last Thursday. With a sequin-strewn floor, DJ sets by the MisShapes, and the aforementioned sing-along machine—which tempted Moby and Vanessa Carlton, if not the Brazilian designer—the gala at Skylight Studios turned into a raucous affair, raising nearly $300,000 for the museum's Independent Study program in the process. Among the 1,000-plus exuberant guests, many of whom came in Calvin Klein frocks, were HBO stablemates Chloë Sevigny and Jamie-Lynn Sigler, as well as their Sunday-night rival, Justin Chambers of Grey's Anatomy.

With Eva Mendes by his side, Costa showed off the collaborative pieces he had made with Ghada Amer, Billy Sullivan, and Vik Muniz. The actress was also following Costa's lead on the karaoke front. "I suck at singing. I've only done it once at a bar in Australia," she said, blanking on the song's title. But after some prodding, and the promise of a second glass of champagne, Mendes eventually belted out the chorus to Bonnie Tyler's "Total Eclipse of the Heart."

Across the pond, an equally chic and only slightly less animated crowd gathered at Kensington Palace's Orangery to celebrate the opening of a Roger Vivier shop on Sloane Street. Inside, the walls were decorated with artist Marianne Guely's giant paper cutouts of pink Micol roses (favorites of the French cobbler), while outside images of Vivier shoes by photographer Daniel Jouanneau were projected on trimmed topiary trees. Uma Thurman, Sting, Trudie Styler, Dita Von Teese, Allegra Hicks, and Alice Temperley all lingered in the gardens, enjoying the unusually mild temperatures and mingling with the label's owner, Diego Della Valle, and its creative director Bruno Frisoni. "I'm delighted to meet all these beautiful women," said Frisoni, who regaled the crowd with the story of one in particular, who bought two pairs of shoes that morning, then returned for two more in the afternoon. "They shop as if they are buying little cakes."

—Sarah Cristobal (Art Party) and Nick Vinson (Roger Vivier)