The Harvest Sprites are tiny elves that live in the cave connected to the carpenters' clearing. They are unique in that they all share the same affection value (i.e. you only need to talk to/gift one of them and they all have the benefits; multiple talks/gifts have no benefit). If you get them to high enough affection they will feed your animals on days you forget or aren't able to (sick, typhoons, weddings, certain cut-scenes). They also play an important part in restoring the Vineyard and getting a Power Berry from Stu.