The Blue Spiny Shell (usually called the Spiny Shell and also commonly referred to as the Blue Shell by fans and the media) is an item from the Mario Kart series. Its first appearance is in Mario Kart 64.
The Blue Spiny Shell appears in many Mario Kart games as an item from an Item Box. Its general purpose is reminiscent of a Red Shell, except that it targets the player in first place (or the leader of the race), and inflicts more damage to the targeted racer. Its function varies slightly from game to game. Aside from the Mario Kart games, the Spiny Shell is a power-up in some Mario sports games. It is easily one of the most powerful items in Mario Kart due to the random nature of its appearances, its main function of going after the leading racer, the fact that it is generally unavoidable without the use of certain items, and the utter effectiveness of its attack and blast radius.
Starting from Mario Kart: Double Dash!!, the Blue Spiny Shell is explosive, practically being the "flying" equivalent to the Bob-omb.
A Blue Spiny Shell Collector's item is also available with the Mario Kart 8 Limited Edition bundle as well as the game disc.
New Super Mario Bros.
In this game, the Blue Koopa Shell is a collectible power-up with a priority higher than the Fire Flower but lower than the Mega Mushroom. It attaches a Blue Shell from a Koopa to the body of Mario or Luigi, and, if they achieve a certain speed, they withdraw into the shell, spinning along the ground, though still able to jump. This method of travel is slightly slower than usual but makes Mario invincible to most enemies. It does not provide resistance to any other hazards (fire, spikes, being crushed). Upon colliding with a breakable block as a shell on the ground, it breaks; the shell's direction changes at this or any other collision. Another power it has is if Mario ducks, he will hide in his shell, and no enemies will notice or attack him.
Mario Kart series
In Mario Kart 64 and Mario Kart: Super Circuit, when fired, the Blue Spiny Shell will travel along the middle of the track until it hits the racer in first place, knocking out any racers in its path along the way. Similar to the Red Shell, the Spiny Shell will break if fired at a wall, and it is not able to clear some larger jumps. As other items or racers cannot break the shell, many players find it extremely useful to hold the Spiny Shell behind them indefinitely, thereby protecting them from any items or racers approaching from behind. The only way for the first place racer to avoid being hit by the shell is to use a Star or Boo. Players between the leader and the racer who fired the shell can move away from the middle of the track to avoid being hit.
Since Mario Kart: Double Dash!!, the item’s use was changed significantly and had wings. When used, the shell will immediately fly to the racer in first place, hover for a few seconds, and make contact with the racer to make a blue explosion similar to that of a Bob-omb and make the item thrower drag. When used in first place, the Blue Shell will immediately fly up above the player and drop down as usual.
Mario Kart DS
In Mario Kart DS, there is a trick you can learn that will allow you to dodge Spiny Shells nearly every single time you encounter them. The only real limitation is that you must be able to powerslide, which might not be practical on some parts of certain tracks. Also, you must be playing on 100cc or higher (which includes Wi-Fi).
Dodging shells will be much easier if you have prior knowledge of the shell's existence. If you don't know the Spiny Shell is on the field until you hear it hissing, then you'll have to be much quicker to dodge it. Make a habit of scanning the item list on the bottom screen often so you'll have time to prepare after seeing an opponent launch it.
When the shell finally reaches you, it will hover over your kart for about a second, then spin over your head once, and then eventually drop quickly and explode. Timing is crucial here, so pay attention. By the time the shell is hovering over your head and starts spinning, you should have red sparks. As it finishes the spin, it will pause for a split second in midair before it starts to drop. At this point, turn hard in the direction of your powerslide (so if you were sliding to the left, press left to make your turn tighter). Just as the shell drops, release the powerslide and immediately start a new one in the same direction. If done correctly, the speed boost from the mini-turbo combined with the extra hop from the second powerslide will cause the shell to miss and explode harmlessly behind you.
It takes a relatively good amount of practice to be able to pull this off for the first time, and even more practice to get to the point where you'll dodge them without fail every time, but it's worth it, and it helps a lot in getting three-star rankings in GP. Check out the video to the right for a more detailed tutorial.
A more natural way to dodge the blue shell is to get out of first place before it enters the touch screen.
Mario Kart Double Dash!! and Mario Kart Wii
In Mario Kart Double Dash!! and Mario Kart Wii, it is possible (though difficult) to dodge a Spiny Shell provided you have a Mushroom handy. Just as the shell drops (you have just a few split seconds), activate the mushroom. If your timing is right, the shell will miss and explode harmlessly behind you] Unfortunately, it is very rare to have a mushroom in first place, so this trick is of limited usefulness. If this is the case, you might as well take a couple opponents out with you. When you hear the siren, check your rear-view camera and brake and/or swerve to get near one or more opponents. Hopefully, they'll be inside the blast radius when the shell takes you out. In Mario Kart Double Dash, it is not so smart. In Rainbow Road, the Blue Shell will sometimes miss and will explode behind you without harm. In Mario Kart Wii, the Blue Shell might also miss you when you enter a cannon in Maple Treeway, DK Summit, Rainbow Road, or DK's Jungle Parkway, provided you entered it at the right time. If the shell continues to make the sound while you are in the cannon and it doesn't explode behind you, you have timed it wrong, and the shell will come back for you, although it takes a long time, considering that the distance between the cannon and the destination is usually long. If you drop off the course like N64 Sherbet Land, the shell will fly to that location and will fly around back and forth and then fly back to you and blow you up. You can also destroy these with bananas. If a Spiny Shell comes after you and at the right time you jump a ramp (is rare and best happens at Peach Beach) you can throw a banana, and if lucky, it will hit the shell, and it'll break it before it eliminates you.
Mario Kart 8/Deluxe
In Mario Kart 8 and Mario Kart 8 Deluxe, the new Super Horn power up can destroy any obstacles within its wave, even Spiny Shells. Before the Spiny Shell drops on the first place racer, the player should use the Super Horn, and the shell perishes.
Super Smash Bros. Series
In Super Smash Bros. 4, the Blue Spiny Shell is an item that can be picked up and thrown like most other items. When thrown, the Blue Spiny Shell looms over the fighter who's currently in first place, and seconds afterwards it'll drop down on the fighter, cauing a blue explo
sion, very similar to the Blue Spiny Shell's behavior in the Mario Kart series.
The Blue Spiny Shell also reappears in Super Smash Bros. Ultimate, serving the same purpose as it did in the previous game.