It was missing a piece. And it was not happy. So it set off in search of its missing piece. And as it rolled it sang this song - "Oh I'm lookin' for my missin' piece I'm lookin' for my missin' piece Hi-dee-ho, here I go, Lookin' for my missin' piece.
Shel Silverstein (1976). “The Missing Piece”, HarperCollins