This is the Buu that is hatched out of the egg. He is fat because he absorbed Dai-Kaioshin who was fat himself. The fat Kai also gave Buu a calmer temperment. He manages to kill Dabura, Vegeta tries to do a suicide explosion attack but fails. Buu kills his master and goes around destroying cities. He befriends Hercule (Mr.Satan) and finds an injured puppy and heals it. Someone shoots Hercule and Buu heals him. Buu is talked into not killing anymore and all the evil comes out of his body to form Thin Buu. In this form, Fat Buu has a massive sweet tooth.
This is the same version as Fat Buu, the only difference is that Good Buu is good and weaker too.
Not much is known about this form except that he is darker, taller, thinner, stronger and UGLIER than good Buu. He easily overcomes good Buu and turns him into chocolate, eats him and becomes...
This form of Buu is almost pure evil, he becomes taller and more muscular. He is more serious than all the other Buu's and scarier at that. He can now sense energy and flies to the Kami tower where the Z fighters are. He is able to keep calm and plan things out, sometimes he does silly things for almost no reason at all. You can tell he is somewhat lazy because he always keeps his head tilted to the side and he does not attempt to speak properly. He is evenly matched with Super Saiyan 3 Gotenks but when Mystical Gohan comes he beats Buu up. Buu comes up with a plan to absorb Gotenks and Piccolo. In this form he still has his sweet tooth.
This is Buu when he absorbs both Piccolo and Gotenks. He is more 'humanized' and you can see he now has a nose. He is now very arrogant and very strong. He beats up Mystical Gohan for awhile until Goku comes. There are two versions of Super Buu, the first is when he has Gotenk's jacket. When Gotenk's fusion ends he wears Piccolo's cape.
Super Buu 2
This is what he looks like when he absorb's Mystical Gohan. He is much stronger and less serious, he also has a more profound shaped chin. Vegito is stronger than him but Super Buu absorb's him. He doesn't take on any characteristics of Vegito because he is not digested. In this form Super Buu still has his sweet tooth and often throws out tantrums.
He is called Kid Buu because he has the body of a 10 year old. He is very strong and without the good Kaioshin in his body he has nothing to hold himself back and he attacks ruthlessly. Kid Buu destroy's the earth but the Z warriors are transported to the other world. Kid Buu follows them there and they fight. Kid Buu is finally killed by Goku's Spirit Bomb.
Ubuu is the good but weaker reincarnation of the evil Majin Buu. Goku wishes him back with the Dragon balls. Goku takes teenage Ubuu with him to train and they enter the world's martial arts tournament and they face off one another. Their fighting almost destroys the planet.
This is when Ubuu and Good Buu find out that they were once one and so they fuse to become Super Ubuu. (Creepy) They try to fight a powerful enemy but they die!