That's What Leprechauns Do by Eve Bunting (2009)
What do leprechauns do? They bury a pot of gold at the end of the rainbow, of course. But as Mrs. Bally Bunion’s ox, Miss Maude Murphy’s hen, and Old Jamie soon find out, they can’t resist having a little fun along the way. For, besides burying pots of gold, mischief is what leprechauns do!