Doc Hudson

Doc Hudson (also known as "The Fabulous Hudson Hornet," "Grampa," or simply "Doc") is a character in Cars.

Cars
"Doc Hudson is a car of few words but many talents. He not only serves as the town judge, he's also Radiator Springs' resident doctor. Doc 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."

Doc is Radiator Springs' resident judge and doctor.

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 never to return to the life 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. He was less than happy when Lightning discovers his past. 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 watches 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.

Mater and the Ghostlight
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
Doc won't physically appear in Cars 2. However, it has been confirmed that there will be several tributes in the sequel hinting to him.

According to story supervisor Nathan Stanton, when Cars 2 takes place, Doc Hudson has passed away. He 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]."

Trivia

 * A blue Hudson Hornet can be seen parked on the street to the left of the screen at the 1:40:31 mark in The Incredibles. Even though Cars was released after The Incredibles, development of Cars was well under way, and this is most likely a reference to Doc Hudson.
 * Doc Hudson is a 1951 Hudson Hornet.
 * The Hudson Hornet was one of the first cars used by drivers in the begining of NASCAR.