Book excerpt: One warm, sunny day, Willy the Chimp decides to go to the park. There's not a cloud in the sky--well, except for just a little tiny one. It doesn't bother Willy too much at first. But as the cloud follows him, it grows bigger and bigger and becomes harder and harder to ignore. Pretty soon the cloud is all Willy can think about, and he has no idea how to make it go away.