Doc Hudson is the retired racing champion with the number 51 in Pixar’s Cars.
Doc is introduced as Radiator Springs’ local physician, but Cars later reveals that he was once the Fabulous Hudson Hornet, a celebrated racer. His racing number was 51, matching the number used by the real Fabulous Hudson Hornet.
The character is based on the Hudson Hornet, an American automobile that competed successfully in early stock-car racing. Doc’s backstory explains his impatience with Lightning McQueen: he recognizes the young car’s talent but distrusts the arrogance that once damaged his own career.
Doc Hudson was voiced by Paul Newman in Cars. Because Newman died in 2008, the character appears through archival material in Cars 3 rather than as a newly recorded speaking role.