Entei - Fu Lion (shishi), a stone lion common in Japan’s history, like a gargoyle, that guarded holy places.
Raikou - Raiju, a lightning spirit that can take the form of animals, including tigers.
Suicune - Quilin, a Japanese form of unicorn with a dragonish muzzle, giraffe or leopard spots, and the horns of a deer. It can walk on water and purify it.
Legendary Beasts - not dogs or cats, people.