In the AnimeEdit
In the anime, Buu is a creature as old as time itself that is summoned and controlled by Bobidi and then Babidi. He diligently serves Babidi by destroying whomever or whatever is in Babidi's way.
In Dragon Ball Z AbridgedEdit
So far, Buu has not officially appeared in the Abridged series. He was referenced during Bardock: 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) We all really wish they would. <3