The Missing Piece is a book by Shel Silverstein about a circle with a slice of itself missing. It sings about the missing piece and rolls along in search of it. After finding pieces that don't fit, it eventually finds one that fits perfectly. With the missing piece, the circle can roll faster than ever - but it can no longer sing and it can no longer slow down to appreciate the things it used to (like the company of a worm or butterfly). The circle discovers it felt more complete without the missing piece and begins singing and rolling happily on its own.