Majin

"I'm not Majin Buu anymore, I'm not even Kid Buu. I'm just a...Majin"

- Majin Majin is Kid Buu after he absorbs Goku.

Creation
Even though everyone thought Kid Buu to be dead, he was not. Part of him lived on. After Goku had blasted him with the Kamehameha as his Super Saiyan 3 level, Kid Buu was blown up and came back together, but one part of him was left behind and ended up staying all through out the battle and for many years. After Goku defeated Omega Shenron the small peice had finally made its way to Earth and absorbed Goku, and Goku was to weak to stop it, creating Majin.

History
After the small peice absorbed Goku everyone thought that they would have to kill him but they were all to weak. It was revealed that Goku's pure heart had turned Kid Buu into a good Kid Buu, although it did not make him pure good. He said that he would not kill he only wished to live on Earth and fight.

After a few years he started to become evil but no one could stop him and since Mr. Satan was his best friend, short of, he managed to talk him to becoming good again.

After Vegeta had learned how to go Super Saiyan 5 he faced Majin, and took him on at full force. Eventually both started to get worn down and Vegeta had been saving up his power for an all out energy attack, since the whole battle he hadn't used any energy attacks the whole fight. He charged his Final Flash and completely blew Majin away and there laid the pod with Goku in it. Vegeta powered down and freed Goku who had stated that that way a long nap. They ended up facing Kid Buu next, but it was an easy victory.