Although he is one of the most powerful entities in Dragon Ball Z, Majin Buu is often playful and displays his childish personality, revealing he destroys things for fun simply from old instructions from his master, stopping once told what he was doing was wrong thanks to the Grand Supreme Kai's personality showing in him. Though he is playful and silly, his evil side is readily apparent, especially shown when his eyes widen, and steam shoots out of the holes on his body. He finds enjoyment in taking the lives of many and shows no remorse, though this is because he treats everything as a game. In battle he fights in a bullying manner, using his immense size to outflank his opponent. During his second battle against Gotenks, Gotenks was preparing the Super Ghosts of his Super Ghost Kamikaze Attack for battle. Piccolo showed Gotenks that Buu had already regenerated from the last Super Ghost attack. Super Buu was also lying on his stomach, drinking a soda (though it looked like a milkshake) and reading a magazine, much to Gotenks' fury and embarrassment. Also, when Goku and Vegeta were preparing for battle, Kid Buu was sleeping, much to Goku's surprise.
Despite the pleasure he takes in mass-murder, it is later revealed that he only committed such acts because he was unaware of their morality, and because he had been commanded to do so by Babidi, and Bibidi before him. The Grand Supreme Kai's presence is more influential in this form than in Super Buu, who is mostly evil and is influenced very little by the Kai. He literally struggles with the evil inside himself, with the evil winning and usurping near complete control, Majin Buu becoming far more dangerous as a result. Buu also possessed an enormous appetite for sweets, shown to far exceed even Goku's eating habits, as Buu was still hungry after he once turned a whole city of people into candy and ate them. Majin Buu only has to sleep for about one second to get the results humans get from sleep. He was extremely naive, as he was completely ignorant of Mr. Satan's (inept) attempts to kill him, as well as the fact that Bibidi and Babidi were using him.