Doc Hudson

Doc Hudson (formerly known as The Fabulous Hudson Hornet or simply Doc) is the deuteragonist of Cars.

He is a car of few words but many talents. He not only serves as the town judge, he's also Radiator Springs' resident doctor. He is respected and admired by the townsfolk for the way he looks out for their health and tends to their aches and pains. No one knows too much about Doc before he came to town. He keeps his private life private. But if you've got a bad spark plug or a rattle in your engine, his door is always open.

Cars
He was once one of the most famous racecars in history; he won three Piston Cups, and still holds the record for most wins in a single season. However, it all changed for Doc when he was involved in a terrible crash during the final lap of the 1954 Piston Cup championship race, which saw him put out for the season. Upon his return, he was received with a complete absence of fanfare and told that he was a has-been who had been passed up for the next rookie in line. He kept a newspaper article on the career-ending crash as a reminder to never to return to the career that nearly killed him.

Jaded by the racing scene, he left that world, apparently taking out time to study medicine. The famous #51 disappeared into obscurity, leaving many wondering where he had gone. He instead opted for a simple navy blue paint job and the life of a physician in the tiny town of Radiator Springs, the "shining Gemstone" of the Mother Road - Route 66. He runs Doc's Clinic as a "doctor of internal combustion". As times changed and the town got bypassed in favor of Interstate 40, Doc stayed on, even when the population had dwindled to a meager dozen or so residents. He is respected, well-loved, and serves not only as the town's physician, but as its judge as well. However, nobody in the town had any idea of his past as a racer; he was just an ordinary Hudson Hornet to them.

Upon meeting Lightning McQueen, Doc saw far too much of his past in the rookie. Doc was less than happy when Lightning discovered his past career. After Lightning finished fixing the road he damaged and decided to stay for a while, Doc was unable to bear having him around any longer and called the news and press to immediately take him away to the Piston Cup, declaring that it is best for everyone. But seeing how disheartened everyone was by his unplanned departure, Doc realized that Lightning had become more important to them than he thought. He eventually admits the truth to everyone about his Racecar days and he took back his old #51 colors to become Lightning's pit crew chief, bringing nearly the entire town (except Sally, Red, and Lizzie -- who watch the race on TV) to the Piston Cup to support Lightning as his pit crew (and in an ironic twist of fate, finally received that long awaited fanfare for his return).

By the end of the film, Doc opts to keep his racing colors, and becomes a trainer as well as a friend to Lightning. Just like Lightning, Doc learned some lessons: friendship, promises, how greed affects others, and that secrets can't be kept forever no matter how long you try to keep them.

Mater and the Ghost Light
Doc appears in the short film, where he scares Mater into believing in a monster called the Screamin' Banshee, which actually ends up existing.

Cars 2
Sadly, Doc died prior to the events in Cars 2, but posters of him are still shown in his museum. In memory of him, the Piston Cup was renamed the Hudson Hornet Memorial Piston Cup, and gets a new logo with an image of the Hudson Hornet and the words "Hudson Hornet" above it. It appears prominently on Lightning McQueen's hood. Doc’s office was converted into the Hudson Hornet Racing Museum.

When Lightning was showing Mater his new Piston Cup, they mentioned him a few times. Also, during the race in Tokyo, on the dirt section, Mater told Lightning to do what Doc has taught him (turn right to go left). Which he did and took the lead. The circumstances of how Doc died are unknown, especially considering the fact he's a vehicle.

John Lasseter was at first adamant that Paul Newman would return to voice Doc Hudson, even though he had announced his retirement from acting. After Newman's death, Lasseter said that they would see how the story goes with Doc Hudson. Story supervisor Nathan Stanton said : "we felt, after really tooling around with the idea of him being in the film and how do we properly use him, it just felt right that we should have his character have passed away also [as Paul Newman]." John Lasseter said that he realized "Doc Hudson was Paul Newman. The character was written after listening to him talk about his passion for racing." and that "We pay homage to Doc Hudson, which is paying homage to Paul Newman."

Disney Parks
Doc Hudson appears in Radiator Springs Racers at Cars Land in Disney California Adventure. Set between the two films to allow for his presence, Doc Hudson serves as the crew chief for the guests, appearing in Audio-Animatronic form before the race to offer advice as well as providing radio chatter in the cars while they are out on the track.

His medical office is also part of the dining complex for Cars Land's version of Flo's V8 Cafe.

Trivia

 * A blue Hudson Hornet can be seen in The Incredibles, an easter egg appearance of Doc Hudson. Even though Cars was released after The Incredibles, development of the film was well under way.
 * Doc Hudson is a 1951 Hudson Hornet.
 * The Hudson Hornet was one of the first cars used by drivers in the beginning of NASCAR.
 * Vanellope von Schweetz performs the "turn right to go left" trick on a sharp turn in the Sugar Rush racetrack from Wreck-It Ralph. This may be a reference to Doc's advice that he gave Lightning McQueen: "Turn right to go left."
 * His death prior to the events of Cars 2 is out of respect to the death of his voice actor Paul Newman, who died in 2008.