“Sex and the City” costume designer Patricia Field talks at the movies. The flame-haired fashion plate stole the show when she kept interrupting an exchange between Isaac Mizrahi and fashionisto Derek Blasberg prior to a Grand Classics summer screening of Bob Fosse’s “Sweet Charity” at the W Downtown. Mizrahi, who curated the evening, was discussing New York’s influence on his designs, saying the city has “inspired everything I’ve ever done. This idea of something very raw and ugly next to something really polished and beautiful.” Blasberg dubbed this “gritty glamour,” causing Field to shout out her disapproval from the audience. “It’s nothing new, you know! It’s just our time’s reinterpretation . . . gritty glamour was in the 1940s in the war, it was in the Depression!” Mizrahi managed to respond to the one-woman barrage with a faint, “Maybe.” When Mizrahi then mentioned seeing nude scenes in the movies his parents took him to when he was probably too young for it to be appropriate, Field shouted, “Me, too! My parents, too! It was no big deal. Life!” Blasberg — who wrote the advice book for young girls “Classy” — came to Mizrahi’s defense, countering, “It is a big deal.”