Turtle-like enemies from the Mario series, with shells that come in many different colors. Flying variants are usually called Koopa Paratroopas.
Koopas, along with Goombas, are some of Mario's most persistent foes. They're common enemies in the Mario series, usually displayed as foot soldiers of the Koopa Troop, under the direct leadership of Bowser. Since Super Mario 64, however, many Koopas have appeared who do not work for Bowser (or any other villain), some of whom even act as allies to Mario during his adventures.
In Japan, the Troopas are referred to as "Nokonoko".
