Hippopotamuses, often abbreviated to hippopotami or hippos, are stout, naked-skinned, and amphibious artiodactyl members (and the only living members) of the family Hippopotamidae possessing 3-chambered stomachs and walking on 4 toes on each foot. While they resemble pigs physiologically and are pseudoruminants like camels, their closest living relatives are actually the cetaceans (whales and dolphins).
There are 2 living species of hippopotamus in 2 genera; the pygmy hippopotamus (Choeropsis liberiensis) of the forests of west Africa, and the hippopotamus (Hippopotamus amphibius).
Hippopotami appear in several episodes (and 1 joke).
Several more hippos appeared in "Funny Faces".