Cattos as a species are cat-like creatures composed of a head, torso, and cat ears. Most Cattos have big, white eyes that are devoid of pupils, and a cat mouth. They all resemble an element of the Periodic Table in some way.
Nickel is a silvery-gray Catto with mint green stripes around his head and torso, with a mint green tuft of hair in between his ears. His cheeks and neck are also fluffier than the rest of his body. The letters "Ni" are on his torso.