Lightning (also known as Thunderbolt, Thunder, Storm, Shock, Zapper, or EMP) is a powerful attack Item that appears in all games in the series. Racers will receive these when they're either in, or close to, last place.
When the Lightning is fired, all the racers except the user will be electrocuted by a sudden electric arc that appears over them, making it a great recovery Item. When they are struck, they spin out, lose any of their Items (in Mario Kart: Double Dash!! onwards) and shrink down to a smaller size, slowing them down. The effect wears off after a different amount of time depending on the game and which position the victim is in. In some Mario Kart titles, if a player has been electrocuted by Lightning and a regular sized character runs you over, the racer will get squished, losing even more speed.
In Mario Kart 64, if the player runs over a player who is small while he or she is big, they will be squished for a while even if the launcher is a lightweight and the lightning-stricken player is a heavyweight. If two small people run into another they both will be squished. If they hit an obstacle such as a Thwomp they will be pushed back and be squished.
In Mario Kart: Super Circuit, when this item is used, the music stops playing and then restarts after all shrunken drivers return to normal size. The shrunken drivers will spin out if coming into contact with another driver.
In Mario Kart: Double Dash!!, it won't affect the player if he or she is currently indisposed (such as having just been hit by another item or fallen off a cliff).
In Mario Kart DS and Mario Kart Wii, the effect of being hit by a Lightning wears off quicker the lower in the rank you are. For example, someone hit by one while in 7th/11th place will return to normal almost immediately, while those in 1st or 2nd place will remain shrunk for much longer. Also, the background music of the track will be sped up and raised in pitch. In Mario Kart Wii, a racer who is super-sized from using a Mega Mushroom will be returned to normal size when struck by the Lightning instead of shrunken completely. There are also two items (POW Block and Thunder Cloud) that act similar to the Lightning, but with a few differences. If the Lightning is used in a team match, it will only affect the players on the opposite team. In Mario Kart Wii, the Lightning can appear in Battle Mode, but it will neither pop the victims' Balloons nor give the user any points.
In Mario Kart 7, Mario Kart 8 and Mario Kart 8 Deluxe, the Lightning acts similarly as in Mario Kart 64, in the fact that racers who are small can get run over. In Mario Kart 8 only, the victim will lose their Items even if they were under the effect of a Star at the time. The Lightning can also appear in Battle Mode in Deluxe, but it will not pop the victims' balloons, nor will the user get any points from it.
In other games
The Lightning was an item featured in Super Smash Bros. Brawl and Super Smash Bros. for Nintendo 3DS/Wii U. If a fighter touched it, either they, their opponents, or everyone would shrink, or they, their opponents, or everyone would grow.
- In all Mario Kart games (with an exception of Super Mario Kart, Mario Kart: Super Circuit, and Mario Kart 7), all the voices of the characters affected by the Lightning will be more high pitched. However, in Mario Kart 7, the kart's sound will get extremely high-pitched.
- When Mario Kart 64 was released on the Wii Virtual Console, the flash coming from the lightning was less intense, most likely to avoid seizures.
- More than one person can hold this item at once. This allows for 2 lightnings to appear at the same time. In later games, even three can appear at the same time! An example of multiple lightnings can be found here
- A common YouTube meme surrounding the Lightning is a voice clip from this video playing whenever the player successfully avoids taking damage from the Lightning. This voice clip is frequently used by Mankalor, the publisher of the video in the previous point.