Duff joins cast of new Polish brothers comedy ‘Stay Cool’. Hilary Duff has joined the cast of the new Polish brothers comedy ‘Stay Cool’. Duff will co-star with Winona Ryder, Mark Polish, Sean Astin, Chevy Chase and Jon Cryer. The project, which shoots in July in Santa Clarita, Calif., is described as a “knowing-your-age comedy,” centering on a successful author (Polish) who is forced to confront an unrequited high school crush (Ryder) when he returns home to deliver a commencement address to graduating seniors. Duff will portray Shasta O’Neil, a sexy high school senior who flirts with the visiting author and invites him to the prom. Mark and Michael Polish, who wrote the script, are producing with Jonathan Sheldon, Ken Johnson and Janet DuBois. Michael Polish is directing.