Old Yeller is the title character in the movie of the same name. He's a Mastador and a hero. At first, he caused trouble such as scaring Travis' mule, Jumper, and stealing food from his family, which angered him deeply. However, after he saved his younger brother, Arliss, from a mother bear, Travis changed his mind and grew fond of him. They became good friends and worked together to keep the farm in order and safe. However, one night, when a wolf attacked, he was bitten during the fight and unfortunately got rabies as a result. Travis was distraught about this and reluctantly had to shoot him to put him out of his misery. Afterwards, he made a grave for him and buried him in it, then he started raising his son, Savage Sam, planning to make him just like his dad.
When he had rabies, Old Yeller's growls and snarls were really recycled sound effects from Tramp, from Lady and the Tramp, when he was fighting the rat.