Hippo cow

The Cow Hippo is a very large, meat-eating domesticated animal. The Cow Hippo is first seen in "The Headband". Aang later has a nightmare about Fire Lord Ozai riding a flying, fire breathing Cow Hippo in "Nightmares and Daydreams".

Anatomy
The Cow Hippo is mostly white with irregular black spots on its skin, small horns and floppy ears. It has the head of a hippopotamus and the body of a cow, with short, stubby legs that end in hoofs. The Cow Hippo also has udders.

Connection
The Cow Hippo has the body shape of the real life hippopotamus. The horns, udders and colors of the Cow Hippo are that of a Friesian cow. Despite the fact that both of its namesakes are herbivorous, the Cow Hippo eats meat.