Peek-a-boom

A Peek-a-boom is an ninja-like enemy appearing in Wario Land: Shake It! Its name is a pun on the phrase "Peek-A-Boo" and the exploding sound "Boom".

At first, it is invisible. If Wario comes closer, it appears with a cloud of smoke, but if Wario comes too close to them, it vanishes again with more smoke. These enemies throw bombs to attack Wario. Sometimes, Wario needs these bombs to solve puzzles, which let him get to treasures. If Wario uses an Earthshake Punch when he is close to a Peek-a-boom, he can pick it up and shake it.