Besides having designed some of the most inventive and deeply American fashions of the 20th century, Isaac Mizrahi is also a man of the stage. He’s designed costumes for plays, dance, and opera, has starred in cabaret and a one-man show Off-Broadway, and has made guest appearances in a number of television shows. Mizrahi is an ebullient and witty raconteur, which makes his three-week stint in the long-running musical Chicago intriguing. He’s stepping into the role of Roxie Hart’s malleable husband Amos Hart, who has a way of disappearing into the scenery and whose monotonal solo song is called “Mr. Cellophane.” Isaac as Amos? Never underestimate the gifts of Mr. Mizrahi. —Laura Jacobs