So, for the scenes in which Cujo rams his head into the car window in an attempt to break through, a mechanical dog and dog head were used. Additionally, for some of the more involved scenes, stuntman Gary Morgan performed these scenes wearing a dog suit to keep both the dogs and the actors safe.

How did they make Cujo mean?

The foam around Cujo's mouth was made of a concoction of egg whites and sugar. The dogs caused problems on the set by constantly licking off the tasty mixture. Stephen King has admitted several times that he was so deep into his alcohol addiction at the time that he does not remember writing the book.

Were any dogs hurt in the making of Cujo?

The main dog featured sadly suffered an untimely death due to an infection during post-production, and the names of all the dogs who appeared in Cujo have been lost in the fog of time.