Blue Shell

Blue Shells are blue Koopa Troopa shells that first appeared in Super Mario World. This was one of the only games they were worn by Koopa Troopas. The Koopa Troopas wearing Blue Shells were just like Koopa Troopas wearing Red Shells. They 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. They also walked faster. They are a rare type of shell, even rarer than Red Shells.

Like other Koopa Troopa shells, the Blue Shell will be launched when the Koopa Troopa wearing it is jumped on. It 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 or Buzzy shells, which are darker and more spherical. During the events of Super Mario World, Blue Shells give Yoshis wings that allow them to fly until it swallows the shell or spits it back out, in which case it will behave like a green shell does, flying out at high speed and knocking over all enemies in its way.

In the Mario Kart Series, they are deadly weapons. They are similar to Red Shells, except these home in on the driver currently in first place. In Mario Kart games made after Mario Kart Super Circuit, Spiked Shells are replaced with the Flying Spiked Shells, most likely because of their low reliability in Mario Kart 64 and Mario Kart Super Circuit. They could be missed and fired at a wall, but would otherwise never fail in hitting the target. They would sometimes crash into a wall, if fired near a curve and were unable to make certain long jumps. These varieties were spiked and called Spiked Shells.

The flying versions of these were called Winged Spiny Shell. After firing one, it flies over the course, homing on the current contestant in first place. After the shell reaches its destination, it will hover for a brief moment over its target, then smash into the ground, giving off a massive shock wave causing the target and anyone near him to bounce around out of control. Winged Spiny Shell are much more efficient than the previously replaced Spiked Shells. These shells have appeared in Mario Kart: Double Dash!! and Mario Kart DS. The Winged Blue Shell will also appear in the upcoming Mario Kart Wii for such home console.

In Super Mario Strikers, as well as in Mario Strikers Charged, Blue Shells appeared as items. They are usually collected in a pack of three. When used, they will be fired at the opposing players, however, they do not home in, like the Red Shell does. If the Blue Shell happens to hit a player, they will instantly freeze in one spot. This will render them unable to move, and, thus, unable to get the ball. The effects wear off after a few seconds. Unfortunately, these shells can freeze both the users teammates, or the user him/herself. If the shells fail to hit anyone, they will continue bouncing around the stage until they either hit a player, or just wear out on their own. A more effective version of this item, is the Giant Blue Shell.

In New Super Mario Bros. there is a Blue Shell but it is not used as a weapon but as a Power-up. The shell turns Mario or luigi into Shell Mario or Shell Luigi respectively. The shell version of Mario or Luigi looks much like a Koopa Troopa with a blue shell. When ducking, shell Mario/Luigi cannot be hurt by almost anything. A blue shelled Koopa Troopa who emits blue shell power-ups when stomped appears in multiplayer. It regrows one periodically. A Blue Shell (taking its appearance from Mario Kart: Double Dash), referred to as Spiny Shell, appeared in Super Smash Bros. Brawl as a sticker. If used in the Subspace Emissary, the sticker would increase the launch power of a specific character by eleven.