Buu is introduced in the series during the Buu Saga as an innocent-looking, pudgy, pink genie-like creature. Later, it is revealed that Buu's original form is a sleeker, child-like version known as "The Boo of Pure Evil." However, his nature and form were altered after he assimilated the gentle, pudgy god (Dai Kaioshin) into his body. Buu's creator, a wizard named Bibbidi, used Buu to wage war against the Kaioshin. Buu managed to assimilate two out of the four Kaioshin; the second one changed his nature to become more innocent. Before this, he had killed the third Kaioshin. After Bibbidi sealed Buu away, he was killed by the fourth Kaioshin, and Buu was transported to Earth where he remained dormant for five million years until he was revived by Bibbidi's son, Babbidi, during the events of Dragon Ball.
When Buu first emerges from his shell, he is tall, round, and has a naive and innocent personality. In this form, he kills Babidi but soon befriends a human named Mr. Satan and later heals a puppy he names Bay (Bee in English). Despite his change of heart, two gunmen destroy his house and attempt to kill Bay and Mr. Satan. This enrages Buu, causing another form of Buu, known as "The Buu of Pure Wrath," to manifest.
After battling the superior Buu of Pure Wrath, Buu is absorbed, creating Super Buu, who then seeks out Piccolo and Gotenks. After absorbing them, Buu faces Son Gohan. Following Gohan's absorption, Buu confronts Vegetto, who forces him to separate from all the absorbed characters, including Good Buu. Consequently, Buu reverts to his purest form, the original child state called "The Buu of Pure Evil." After a long and intense battle, Son Goku, Majin Buu, and Vegeta ultimately defeat Kid Buu.
