Series is a little younger than some of the other titles on the list., Two volumes are available with two more planned for 2013-14., Hilarious. Even the fart jokes.Six-year-old Leopold doesn't want to go to school one morning. Luckily, it's also the morning he discovers he can turn invisible. His only problem is that he hasn't figured out how to turn his clothes invisible too. Having visible underwear gets in the way of the pranks he'd like to play...