A Zombie Goomba is a Goomba that has risen from the dead. In the series in The Super Mario Bros. Super Show, they first appeared in a Dracula themed episode of Super Mario Bros. 3, "Count Koopula" but are yet to appear in a game.
Zombie Goombas have yellow eyes, maroonish bodies, and dark brown feet. Not much is really known about Zombie Goombas other than the fact that they are Goombas that have risen from the dead and that they still serve Bowser, but they only appear in "Count Koopula". They are believed to be Goombas that Mario has stomped and killed.