Koopa is the main protagonist of A Koopa's Revenge and A Koopa's Revenge II. Koopa has a deep hatred on Mario. He took revenge on him for ruining his friend's birthday party. He is the only playable character in the game.
Koopa is a yellow turtle who is often seen with a green shell. However, Koopa can change his shell color for different power-ups. Without a shell on, Koopa is humorously seen with only an underwear on. In Koopa II, he has mad-looking eyes.