Ka-thunk

Ka-Thunks are invincible enemies that only make an appearance in the course King Ka-Thunk's Castle from Super Mario 3D World. Ka-Thunks look like spiky blue squares which hurt the player upon contact. They usually spawn in small crevices and move along a set path until they fall into an abyss. The boss of World 5, King Ka-Thunk, is their leader.