Cujo the dog

Cujo is a fictional dog and the titular antagonist featured in the 1981 horror novel Cujo by author Stephen King. The character was also the main a-hole featured in the 1983 film adaptation of Cujo. An actual dog was used for most scenes in the film, but for shots where the animal physically interacted with other actors, stunt double Gary Morgan donned a big fluffy dog costume and romped around on the set.

Biography
Cujo was a male St. Bernard dog owned by Joe Camber and his wife Charity, and son Brett. One day, Cujo was chasing a rabbit through a field and pursued it towards a hollowed out log, which entered into a cavern. Cujo poked his head through it and his incessant barking awakened a bunch of bats that were sleeping in the cave. One of the bats bit Cujo on the nose and gave him rabies.

Within a few days, Cujo went completely rabid. He attacked and killed his master, Joe Camber, and later took to munching on Joe's neighbor, Gary Pervier. His next victim was Castle Rock's sheriff, George Bannerman.

Donna Trenton and her son, Tad, drove Donna's Pinto out to the Camber property in the hopes that Joe could make repairs on the car, which had now just died. Cujo terrorized the two of them, forcing them to remain in their car. Tad began hyper-ventilating from heat exhaustion as it had become the hottest day this section of Maine had seen in quite a number of years.

Desperate to save her son and escape the ravenous dog, Donna Trenton made a break from the car and picked up a baseball bat that had been lying on the ground. She beat Cujo repeatedly with the bat until it broke, then took the sharpened broken piece and stabbed him with it until he died.