Famously, most of the cast of Grease was at least a decade older than their characters. Olivia Newton-John was 29 when she played Sandy, Jeff Conaway (Kenickie) and Barry Pearl (Doodie) were both 28, Michael Tucci (Sonny) was 32, Didi Conn (Frenchie) was 27, and Jamie Donnelly (Jan) was 31.