Majuub

Majuub (formerly known as Uub) is a fusion character from the Dragon Ball universe.

He is voiced by Sean Michael Teague.

As Uub
Uub is the positive reincarnation of the evil Kid Buu. He first met Goku at the 28th World Martial Arts Tournament at age 10. He entered to win the prize money to buy food for his starving village. During his round with Goku, he proved to equal Goku in power. After the two forfett the rest of their match, Uub brought Goku back to his village to become his mentor in becoming a Z Warrior.

Ten years later, Uub had become much stronger due to his training with Goku. Uub completed his training after a tiring session with Goku at Kami's Lookout, with the latter stating that he hadn't been this tired since Frieza.

After Goku was presumibly killed by Baby Vegeta, Uub attempted to stop the latter himself. Before Baby could finish Uub off, Uub was saved by Majin Buu, and perminently fused with him, becoming Majuub.

As Majuub
Majuub is the result of perminent fusion between Uub and Majin Buu. His power matched Baby Vegeta and had inherited all of Majin Buu's abilities. After fusing, Majuub became more powerful than he was previously.