The Thunder Cloud (also known as a Lightning Cloud or even The WORST Mario Kart Item by some people) is an Item. It only appears in Mario Kart Wii (due to being heavily criticized), and has a hot potato-like nature.
When this double-edged sword is picked up, the Thunder Cloud will appear above the player, speeding their vehicle up by a notable amount and negating off-road penalties completely. After a short amount of time, however, the cloud will zap the player with lightning, just like the Lightning item, leaving them wide open to incoming attacks or other racers. The cloud may disappear when the holding player travels through a cannon or uses an invincibility item. The item may also be passed on from person to person; the duration of the cloud does not reset when passed, allowing daredevil racers to hold onto the cloud for a very long time to catch up and then bump into another player just as it is about to strike.
- 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.