Captain Underpants and the Perilous Plot of Professor Poopypants - Dav Piley

This book was about a Principal that turns into a superhero with underpants. The only way to stop him is to pour water on his head. Harold and George write comic books on Professor Poopypants the mad sceintist. Some of their tricks get them into a lot of trouble. Once one of their tricks nearly took over the whole world. My favourite bit was the flip-o-rama.
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