Cujo

Cujo is the titular main antagonist of Stephen King's novel and its 1983 film adaptation of the same name, and a minor antagonist in Cat's Eye. He was once a friendly and playful companion, but when he got rabies, he went insane and was turned into a killer that attacked anybody who came near.

He was portrayed by Moe and his vocal effects were provided by Frank Welker, who also played Mor'du in Disney/Pixar's Brave.

History
Cujo was once the beloved St. Bernard of the Camber family, but was bitten by a rabid bat in the nose when his head got stuck in a bat cave while chasing a rabbit (which was shown at the beginning of the movie).

Cujo then went mad with rabies and killed any person he came across including one of his own owners, conducting a murderous reign of terror on Castle Rock.

In the end of both the book and movie, Cujo was seemingly killed by Tad Trenton's mother Donna (who also tried to save her son from dying of ), by being shot by the sheriff's gun. In the novel, he was killed after being hit by a baseball bat.

Along with Christine, he makes a cameo appearance in the 1985 film Cat's Eye where he chases the titular cat, General. This might hint that Cujo was back to his old, friendly self.

Personality
Cujo is given some more insight in the novel while the film portrays him as merely a dog gone mad due to rabies. It is said in both versions that Cujo was friendly dog that loved to play with the local children. After being bitten by a bat and unknowingly infected by the virus, he was afraid his master would be mad and think he was a bad dog showing how much he thought of his owners and their opinions. Cujo, when infected, starts to slowly lose his mind to where he could no longer recognize even his owners (the young Brett Camber) as human seeing them akin to actual monsters barely recognizing his voice and fights off the urge to kill the boy by leaving.

Based on Cujo's perspective, he seemingly only identifies them through small descriptions in all caps like: "THE BOY" and "THE MAN" when thinking of them. As the book progresses, we see that he does not kill for pleasure but due to some of their loud noises and other habits which intensifies his pain thus making him lose what little restraint he manages to retain. Cujo wants to be left alone after being infected to the point he is willing to kill those around him if needed. As his mind continues to deteriorate, Cujo becomes more violent and insane from the pain and starts to believe it is the people around him causing him to be sick. It should be noted that Cujo is not a creature with malicious intent. In fact, the book's ending makes it clear that Cujo himself only ever wanted to be a good dog who after his infection it drove him insane and was no longer in full control of his actions.

Victims

 * Gary Pervier: Neck bitten out.
 * Joe Cambers: Face ripped off.
 * George Bannerman: Knocked off of catwalk and mauled.
 * Tad Trenton (novel only): Sunstroke from being trapped in car.

Trivia

 * In some scenes of the film, a painted rottweiler was used since actual St Bernards where not capable of performing convincing simulated attacks. The Rottweiler's tail was strapped to its leg to prevent it wagging and undermining the sense of fear.
 * To make the dogs attack the car in the film, their favorite toys were placed in the car so they would try to get them.
 * There was an early draft where Cujo was also going to be possessed by a spirit of a serial killer, but was scrapped because it was seen as too outlandish and would detract from the fear the writers wished to portray in the film.
 * The dogs featured in the film would often have their tails tied down to their legs, because the dogs would be enjoying themselves so much that they would wag their tails during filming. This tactic was missed once in the editing where they show Cujo from behind ready to attack and his tail is wagging energetically.
 * A rumor has circulated that "Cujo" is an ancient Indian word meaning "unstoppable force". In reality, Stephen King made it up himself when writing the novel.