The Journey of Nils with the Wild Geese by I. Pankov

Nils Holgersson was an ordinary boy, only very lazy, capricious, and mischievous. For one bad deed, the household gnome shrank Nils to tiny sizes. All the domestic animals turned away from the former bully, and Nils set off with the wild geese on a great journey through Sweden, teaching him to be responsive, brave, and appreciate true friends.