King Ka-thunk

King Ka-thunk (known as King Kathunk in the British English version) is a boss that appears in Super Mario 3D World and its Nintendo Switch port Super Mario 3D World + Bowser's Fury as the boss of World 5-Castle: King Ka-thunk's Castle. He is a small, blue metal square with red shoes and detached red hands. He also has five spikes on the front (one of which is positioned like a beak right below his eyes) and his back is pink and fleshy with a bandage on it. King Ka-thunk floats in the middle of another, larger Ka-thunk frame.

He serves as the boss of World 5. His main attack is moving around the Ka-thunk frame before finally stopping in one of the corners. After this, the ground that King Ka-thunk will fall on glows red before he crashes into the ground, damaging any players caught under him or his frame. To damage King Ka-thunk, the player has to jump on his backside while he is facing down. Oddly enough, he is not damaged if a player is thrown onto his weak spot by another player. After each hit, two of the arena's corners will fall off, and King Ka-thunk will become faster and more erratic. Once three hits are landed, King Ka-thunk is defeated, several circles of Coins appear, and the Warp Box to the Goal Pole is revealed.

King Ka-thunk later reappears as one of the bosses in World Flower-12: Boss Blitz with the exact same strategy from his first battle in World 5.

Trivia

 * King Ka-thunk's method of attacking is very similar to that of the Whomp King.