This selection for the Mock Caldecott was scary, then fun. Illustrated by Jon Klassen and created with gouache and then the rest is digital. So, from what it looks like he used the gouache for the background and the splattery textures. The line art and main colors (like the boy and his blue pajamas) are all digitally drawn later. A fun method and a cute book I really liked it, but it wasn't the beeeeest!