Atomic Boo

An Atomic Boo is a large enemy in the video game Paper Mario: The Thousand-Year Door. In the game, he would appear if Mario smashed the Boos surrounding him twice. Thankfully, the enemy is an optional boss that Mario doesn't in fact have to fight. An Atomic Boo will form when exactly 200 regular Boos attach to each other. Once they do, the fight will start. If Mario is able to defeat the boss, then all of the Boos in the Creepy Steeple will leave for good, and the plumber will obtain a special badge.

His heart power is forty, attack is four, and defense is zero.