Good Buu

Majin Buu is a character from Dragon Ball Z that started as an adversary of the protagonists. He was created by Bibidi many years ago as an ultimate killing machine that would enable Bibidi to conquer the universe. However, he was able to be sealed inside an egg and buried deep in the earth. In the present, Babidi, Bibidi's descendant, revives Buu and commands him to begin a rampage of death and destruction across the planet. After proving too powerful for the Z fighters, Buu murders Babidi when he grows tired of following his orders, and continues his destruction spree.

The supposed world martial arts champion Hercule later approaches Buu and convinces him that killing and destroying is wrong, and Buu decides to stop doing it. The two become friends, but not long after, a gunman nearly kills Hercule and a dog named Bee that the pair had adopted. Seething with anger, Buu expels a cloud of steam, which forms into Evil Buu, a manifestation of all of the evil that existed in Buu's heart. The two Buus fight, but Evil Buu turns Buu into chocolate and eats him, transforming Evil Buu into Super Buu.

Much later, as the Z fighters, Goku and Vegeta are fighting Kid Buu, a later transformation of Super Buu, Hercule scolds Kid Buu, who is unable to kill Hercule due to the affection the original Buu once felt for him. Kid Buu then expels the original Buu, who in turn fights against Kid Buu on the side of the Z fighters. After a prolonged battle, Goku is able to destroy Kid Buu with a Spirit Bomb, and he and Vegeta discover the original Buu, barely alive. After some debate, Goku and Hercule convince Vegeta to spare Buu, since he helped them fight Kid Buu and the evil has been expelled from his heart. Buu then becomes a permanent Z fighter and lives with Hercule.