Whimsey

noun

1. A quaint and fanciful idea; a whim; playfully odd behaviour.
2. An impulsive, illogical or capricious character.
3. A whim (capstan or vertical drum).
4. A jigsaw puzzle piece that has been cut into a recognizable shape, as if on a whim; often the shape is representative of the theme of the image used for the puzzle.