Selma Lagerloef 
Wonderful Adventures of Nils 

Nils is a young lad who likes nothing more than eating and sleeping. He is also a very mean little boy who likes to torment animals. One day he catches a tomte who turns Nils into a tomte, which leaves him shrunken and able to talk with animals, who are thrilled to see the boy reduced to their size and are angry and hungry for revenge.