In Rocky, Butkus is Rocky Balboa’s pet dog.
Butkus is a large bullmastiff who appears as Rocky’s companion in the original film. The dog belongs to Rocky in the story and is seen in his apartment and during parts of his everyday life. Butkus helps establish Rocky as an ordinary working-class character rather than only a boxer preparing for a title fight.
The name has an unusual connection to Sylvester Stallone. Stallone owned a bullmastiff named Butkus in real life and included the dog in Rocky. The animal therefore functions both as a story detail and as a personal element drawn from the actor-writer’s life.
Butkus is different from Cuff and Link, the pet turtles kept by Rocky in the first film. The turtles are associated with Rocky’s small pet shop visits and are separate animals from his dog.