Koopas are common enemies in the Mario Franchise, usually displayed as foot soldiers of the Koopa Troop, under the leadership of Bowser. Since Super Mario 64, however, many Koopas have appeared who do not work for Bowser, some of whom even act as allies to Mario during his adventures. Koopa Troopas are turtle-like creatures with removable shells that come in many different colors, with red and green being the most common. Koopas are popular for the many different uses of their shells in the Mario series, notably in Mariokart, where one can shoot them at opponents.