Happiness Rating
From PinataIsland.info, the Viva Piñata wiki
Each pinata resident in your garden has a happiness rating, that reflects the quality of the care that you have been providing for it. If you do not keep your pinatas satisfied then, they will hit the road and return to the wild. The happier the pinata, the more coins it is worth.
A pinata's happiness is measured in the expression on the face that appears when you select a certain pinata.
