Majin Buu (also known as Fat Buu, Evil Buu, Super Buu, Kid/Pure Evil Buu, Good Buu and Mr. Buu) is a character from Dragon Ball Z, who serves as the main antagonist of the Majin Buu Saga in several different incarnations. He was planned to be the overarching antagonist of Season 4 of Dragon Ball Z Abridged prior to its cancellation.
In the Anime
In the anime, Buu is a creature as old as time itself which is summoned and controlled first by, Bibidi, and then his Babidi. He diligently serves Babidi by destroying whomever or whatever is in Babidi's way.
In Dragon Ball Z Abridged
Buu never officially appeared in the Abridged series, though he was referenced in Bardock, the Father of Goku during Bardock's final flash forward, in which he sees his son fighting a "weird bug-man" (Cell) and a "fat pink man-child" (Buu). Majin Buu made his first (and to date only) apperance in the Dragon ShortZ special episode A SHORT Halloween.