On Madison Avenue, Calvin Klein's Francisco Costa hosted the likes of Michael Stipe, Simon de Pury, and Vogue's Hamish Bowles at an in-store soirée for Diana Widmaier Picasso, granddaughter of the famous artist. The striking brunette was in town from Paris to sign copies of her new tome, Picasso: Art Can Only Be Erotic. "Francisco fell in love with my book over the summer and decided that we should do something in the store," she said while fans circled around. "After all, we're both about the female form."

Two blocks away at Bergdorf Goodman, another tight-knit fashion circle gathered around Yves Saint Laurent creative director Stefano Pilati. Making his first foray into the New York social scene, he was mobbed by everyone from models (Linda Evangelista, Helena Christensen, and a freshly blond Mariacarla Boscono) to mono-moniker musicians (Usher and Amerie) to girls about town (Amanda Cutter Brooks, Ahn Duong, and Lauren duPont). "What fun it is!" said the man of the hour about the crowd that had gathered. "They are telling me they like my work, and I'm telling them it's the opposite: I admire you!" As for his stay in the Big Apple, the debonair Italian, who eschewed air kisses for gentlemanly pecks on the hand, said that he doesn't really have a base in the States… yet. "I haven't had a real success here," he said. "I am always looking for the next step."

At the close of the cocktail hour, the evening continued at the penthouse suite of Trump Tower with an intimate dinner for 40, including latecomers Julianne Moore and Kanye West.

—Sarah Cristobal