Marko is a plump, friendly rat with steel grey fur, lightening to ash grey for his ventral fur, which goes all the way down between his legs. He has pink ears, nose, tail and paws. He has green or greenish-brown eyes. His prominent buck teeth are a slightly yellowish white.
He prefers being drawn with digitigrade legs but it is up to the discretion of the artist. His long tail has a kink in it, about two-thirds of the way down.
Marko has three whiskers on the right side of his snout and two on his left.
Marko prefers to be drawn without clothing, as he is most comfortable that way.