The World's Best Karlsson by Astrid Lindgren
Smidge is used to Karlsson, the funny little man with a propeller on his back, living on the roof. They are firm friends. Now, anytime Karlsson pops in, Smidge knows that there's fun and adventure in store. In this collection of stories, they flood the bathroom, celebrate Karlsson's birthday, and Karlsson is mistaken for a spy!