Picori

A race of small creatures who tend to help other beings.  They were first discovered when the Hylians returned to the surface, and established their kingdom of Hyrule.  A portal opens once every century, allowing Picoris to grow up to Hylian size, but the portal also works the other way around.  Aside from the evil Vaati, all Picoris are nice and happy when they help others.  It is them who place rupees in the grass, for Hylians to find.