The Bombchu first appeared in The Legend of Zelda: Ocarina of Time and have appeared in Majora's Mask, Oracle of Ages, Oracle of Seasons, Phantom Hourglass, and Hyrule Warriors. In Ocarina of Time and Majora's Mask, Bombchus move forward, crawling up walls and even ceilings, and explode upon impact on an enemy or obstacle, or after a period of time. In Oracle of Ages and Oracle of Seasons, they lock onto an enemy and follow it if there is one present. In Phantom Hourglass, Bombchus follow a given path made by the player. Bombchus in Super Smash Bros. 4 are based off the Bombchus in Ocarina of Time and Majora's Mask as it only moves in one direction.
Etymologically, its name is composed of bomb and chu, Japanese onomatopoeia for a mouse's squeak.
Bombchus appear as a throwable item. Once thrown, Bombchus will keep going at a straight path, traveling over walls and ceilings like a Hothead, and explode upon impact on an opponent; it will pass through the player that used it however. It travels faster over time; if kept for too long, it will start flashing, then explode which can also damage the player who threw it. It will always do 18% damage, regardless of how it is thrown. It does knockback towards the Bombchu's direction.
These mouse-shaped bombs crawl on the ground, up walls, and even along ceilings. If you toss one, it will scurry along until it hits an opponent and explodes. They won't blow up you or your friends—so user friendly! They will blow up if struck, though, so be careful.
These little mouse-shaped explosives run along floors, walls, even ceilings. Throw one and it'll start running as soon as it hits the floor, getting faster and faster. As soon as it touches an opponent, it'll explode. It'll also blow up if you attack it, so be careful if your own Bombchu's passing by.
In Ultimate, Bombchus change their direction when they travel offstage on flat surfaces instead of disappearing, which is a change that Hotheads also have. Like all explosives, directly thrown Bombchus no longer harm the thrower, but it can still harm the user once it starts rolling.