Fly Guy and his human friend Buzz are on a field trip to learn about castles. They discover what castle life was like for the rulers, what the children and servants of those rulers did, what the inhabitants ate, what pets they had, knights' roles, what the dungeons and castle defenses were like, and how castles are used today. Scatological factoids abound: kids will get a kick out of knowing that the person who shoveled poop from the castle toilets was called a gong farmer, or that a catapult was used to fling heavy objects like animal poop upon castle enemies. Impish cartoon illustrations with Fly Guy and Buzz appear throughout. The pages resemble a guidebook with lined notebook paper featuring photos and facts identified and defined with handwritten notes. Inspired by all that they've learned, Buzz and Fly Guy make their own castle at the end sand castle! This nonfiction series entry with its holographic foil cover is fun and informative for Arnold fans.