Hilary Duff has signed on to Stay Cool, which is being billed as a "knowing-your-age comedy", according to The Hollywood Reporter. Duff joins an ensemble cast that includes Winona Ryder, Mark Polish, Sean Astin, Chevy Chase and Jon Cryer. Mark and Michael Polish penned the script, plus they are serving as producers and Michael Polish is directing. The film begins production this July in Santa Clarita, CA. Duff recently appeared alongside John Cusack in War, Inc..