Red Shell
Red Shells are red Koopa Troopa shells that first appeared in Super Mario Bros.. Although not their first specific use, they were worn by Koopa Troopas. The Koopa Troopas wearing Red Shells were a bit more intelligent than normal green-shelled Koopa Troopas. They did not fall off cliffs and simply turned around when reaching a ledge.
Similiar to a Green Shell, the Red Shell will be launched when the Koopa Troopa wearing it is jumped on. In later games, they can also be held and thrown. There are also flying Red Shells which appear in Super Mario RPG: Legend of the Seven Stars. They are not to be confused with Parabuzzy shells.
During the events of Super Mario World, Yoshis can spit out fire while in possesion of the Red Shell. In the Mario Kart Series, they can home in on the opponent whose rank is one higher than the drivers. Red shells can be picked up in singles or triples, in which case they circle around the kart until all three are fired.
