Doc Hudson was formerly a famous Piston Cup champion in Pixar’s Cars.
Known in racing history as the Hudson Hornet, Doc won three Piston Cup championships before a crash ended his competitive career. He later became the town physician and judge in Radiator Springs, where he lived quietly under a different role.
Doc initially hides his racing past from Lightning McQueen. McQueen discovers the truth through newspaper clippings and eventually persuades Doc to help him prepare for the final race. Their relationship forms one of the original film’s central emotional arcs.
Doc Hudson is voiced by Paul Newman, whose own career included major acting roles and a strong association with auto racing. The character is based on the real Hudson Hornet, a car known for its success in early stock-car racing. The King was also a champion, but the question’s former champion who becomes Radiator Springs’ doctor and judge is Doc Hudson.