Operation Mad Ball (1957) marked Hickey's feature-film debut. But the actor wouldn't hit his stride on the big screen until he was nearly 60, earning an Oscar nod for his supporting turn as a Mafia boss in Prizzi's Honor (1985). He also made an impression with audiences in a pair of modern Christmas classics: playing Clark Griswold's feisty uncle in National Lampoon's Christmas Vacation (1989) and a raving mad scientist in The Nightmare Before Christmas (1993).
Hickey also taught acting for more than 40 years, counting respected actors such as James Woods, Billy Crystal, Carol Kane and Tom Berenger among his students. He died on June 29, 1997, at the age of 69.