Cerberus (Disney)

Cerberus first appeared in Hercules and is the guardian of the Underworld that works for Hades in the Hercules series.

Appearance
Cerberus is shadowed and has three heads and red eyes on each head.

Hercules
Cerberus first appeared in the movie, Hercules. He first appeared when Hades rides down the River Styx and he ate a massive steak. Hercules tamed him to get Hades' inner sanctum, though only a temporary turn driven by fear.

Hercules: The Animated Series
Instead of being an adult dog, Cerberus appears as a rambunctious puppy and he is one of Echidna's children, while Hades has difficulties in controlling.

Trivia
Cerberus was the only Hercules monster in the animated film to not die.

Though in Hercules: The Animated Series, Cerberus looks much more like a rottweiler.