Majin Buu is a legendary monster brought back to life by the evil sorcerer Babidi. Buu rebels against his master and kills him, then goes on to kill inhabitants of the earth by turning them into candy.
Buu experiences a change of character when he gives sight to a blind child. This good deed transforms Buu who becomes friends with Mr Satan and a cute little dog. But when two thugs kill the puppy, Buu becomes furious and his body emits so much violence and hatred that it materializes in the form of a new cruel creature, a thinner and brown Buu. The two Buu clash and fight until the good Majin Buu is transformed into chocolate and eaten by thin Buu. The good Buu becomes a prisoner of his evil twin, only to be later released by Goku.