Thunder Cloud

The Thunder Cloud (originally Thundercloud and also known as Lightning Cloud) is an item from the Mario Kart series, appearing in Mario Kart Arcade GP, Mario Kart Arcade GP 2, Mario Kart Wii, and Mario Kart Arcade GP DX. This item works similarly to the Time Bomb in Mario Kart Arcade GP and Mario Kart Arcade GP 2. However, it shrinks opponents rather than exploding. In Mario Kart Wii, unlike other items, it activates itself automatically when obtained from an Item Box, and cannot be thrown, unlike in the arcade games. This item makes a distinct sound when received from an Item Box that is not heard from any other item in the game.

When obtained, the player automatically receives a constant boost of speed. Also, drivers with a Thunder Cloud will not slow down when they go off-road. However, the Thunder Cloud eventually strikes and shrinks the player, having the same effects of the Lightning. The Cloud, however, can be passed on to another kart by bumping into any other racer before the lightning strikes. To use the item efficiently, racers have to bump another player and let them be shrunk instead. It can be destroyed when the character holding it drives into a cannon, falls off the track, uses a Star, a Mega Mushroom or a Bullet Bill.

Trivia

 * The Thunder Cloud is the only item introduced in Mario Kart Wii to not appear in Mario & Sonic at the Olympic Winter Games.
 * Due to the one-of-a-kind nature of the Thunder Cloud, glitches have arisen based on it. Hackers may forcefully spawn multiple Thunder Clouds and pass them onto different players; the previous Cloud spawned in this manner will disappear, but players afflicted will remain boosted for the entirety of the race.
 * The clouds zip sound gets faster as it gets closer to striking.
 * This is the one item in Mario Kart history that activates immediately instead of when you press the button. A buzzer plays when you get it instead of the normal jingle.
 * This is the only item in the entire Mario Kart series you can't drop.

Names in other languages
Wolkenblitz Nuvola grigia