For more information and some other images, go to the Chippy Chipmunk website:
http://www.chippychipmunk.com/
Here's Mo Willems talking about his work as an author/illustrator of children's books:
Non-fiction books often have photographs. This one combines photos and cartoons in a similar way to Knuffle Bunny.
Many science or history-related, non-fiction books contain photographs:
We have the ebook version of the first book of the series if you want to take a look. You will need to authenticate as a KU user for access.
Here's the book trailer that shows some of the images that inspired and are used in the first book as well:
