Majiin Buu/Fat Buu
Originally created by Bibidi, the father of Babidi, to overthrow the Kaio-shins and to destroy the universe. Buu kills almost all the Kaio-shins before he cursed and trapped in a inactive state. His cursed state, or fat form is what emerges when the battle between Goku and Majiin Vegeta takes place, giving enough energy to release him. Gohan and Kaio-shin makes a final desperate attempt to stop Buu before he emerges but are unsuccessful. When Majiin Buu is released, Babidi orders him to begin to destroy the planet. Buu makes his way from city to city, changing people into candy and eating them. Meanwhile, Majiin Vegeta and Goku fight. They agree to finish the battle later in order to deal with Buu. Unexpectedly, Vegeta knocks Goku out and goes to fight Buu alone. His final attempt to defeat the evil menace is to sacrifice himself by self destructing in the hope that the blast will kill Buu. Unfortunately, Buu survives and seems unstoppable. Eventually, Buu gets tired of following Babidi's orders and splits. His Fat form if friendly but weak.

Evil Buu
When Buu spits into two forms the result is his Friendly Fat form and his Evil form. His appearance changes and he is now a darker shade of pink, skinny and is more sinister looking. He battles it out with Fat Buu but is much more powerful than his opponent. Evil Buu ends up turning Fat Buu into a cookie and eats him. The power of the merger allows Buu to transform into his next form.

Super Buu
This form of Buu is much more powerful, taller and leaner. He is more muscular and more adapted for fighting. By this time, Goten and Trunks have been taught the fusion dance and have been able to transform successfully into Gotenks. Buu senses their power and travels to the Sky Palace to confront the powerful being he senses. Piccolo convinces Buu to wait for the boys, who are training in the room of Spirit and Time, to come out of the room. Eventually, Gotenks battles Buu but their fusion wears off and they are absorbed. Buu again goes through another transformation.

Super Buu (with Gotenks)
With the increased power of Gotenks, Buu confronts Gohan, who has returned from his training with Kaio-shin. Gohan changes into his father's style of clothing and battles with Buu. Goku, meanwhile, learns of the Pottera Earrings and plans to fuse with Gohan to defeat Buu. Unfortunately, Gohan is hit by Buu's attacks and drops the Earring. Before they can recover, Buu, who was also hit with an attack, absorbs Piccolo and Gohan and powers up again.

Super Buu (with Piccolo and Gohan)
Buu again powers up and Goku is discouraged. Luckily, Vegeta appears, having being granted life again for his sacrifice, and picks up the earring that Gohan dropped. Goku has to convince Vegeta to fuse with him because the fusion will be permanent. Finally, Vegeta agrees and puts on the Earring. The two fighters are pulled together and Vegitto is formed. Vegitto realizes that the others can be saved and allows himself to be absorbed. The fusion is undone and Vegeta and Goku rescue Gohan, Goten, Trunks and Piccolo. They escape through one of Buu's pores and return to their normal size as they exit his body. Unfortunately, the absorption of Vegitto gives Buu enough power to transform to his original form.

Kid Buu
After the absorption of Vegitto, Buu now has enough power to transform into his original form. Looking more like a kid, Buu is extremely evil and blows up the Earth. Goku and Kaio-shin, who has fused with Kibit, teleport the Z fighters and Mr. Satan to safety on Kaio-shin's planet. Vegeta fights Buu at this point and gets kicked around while Goku attempts to power up enough to defeat the villain. Satan, thinking he is in a dream, confronts Buu and is able to avoid his punches. Suddenly, Buu in obvious pain, spits out Fat Buu and they battle. Of course, Fat Buu is no match for Kid Buu and is beaten unconscious. By this time, the Namek dragon balls have been collected and Vegeta asks for the Earth to be restored and all killed by Buu to be returned. Goku finally defeats Buu when all the people of Earth donate their power and the third wish is used to restore Goku's power.

Ubuu
This is the form of Buu that appears when Goku wishes for Evil Kid Buu to be returned to life and cleansed of all evil. Goku takes over training Ubuu.