Billionaire Peter Brant opened his Brant Foundation Art Study Center on Sunday for a Julian Schnabel exhibition, and the event became a de facto reunion for the cast of Schnabel’s 1996 movie “Basquiat.” The film’s Christopher Walken, Benicio Del Toro and Stella Schnabel were spotted toasting the opening at the luncheon served on Brant’s polo field. The Greenwich, Conn., show also brought out Debbie Harry, Brant’s model wife Stephanie Seymour as well as Schnabel’s fiancée May Andersen and his art dealer son Vito. Further guests included art gods Larry Gagosian, Tony Shafrazi, Gavin Brown, Andrea Rosen, Klaus Biesenbach and Jeffrey Deitch. From the fashion world came Calvin Klein, Nicole Miller and Tommy Hilfiger, while the social and business world were represented by Matthew and Nicole Mellon, Dori Cooperman, Nicky Hilton and Zani Gugelmann.