Doc Hudson is the veteran race car who serves as Radiator Springs' judge in Pixar's Cars.
Doc appears to be a stern local judge and physician, but he is secretly the famous Hudson Hornet who won three Piston Cups. His racing career ended after a crash and a long recovery, when the racing world quickly moved on to newer competitors.
Doc initially dislikes Lightning McQueen's careless attitude and refuses to help him. Their relationship changes when McQueen learns Doc's history and shows respect for his experience. Doc eventually becomes McQueen's chief crew chief and mentor for the final race.
Paul Newman voiced Doc Hudson in Cars. Newman had a major connection to racing outside film: he competed as a driver and co-founded Newman/Haas Racing. Doc does not appear as an active character in Cars 2 because the story explains that he has died, but his legacy influences McQueen in later films.