George and Harold's time-traveling Purple Potty lands them in a crazy place in the eighth book in this #1 New York Times bestselling series by Dav Pilkey, the author and illustrator of Dog Man!

The teachers are nice, the cafeteria serves delicious food, and the school principal, Mr. Krupp, thinks George and Harold are hilarious. Something is very, very wrong — and it gets even wronger when the boys' pet pterodactyl, Crackers, and Sulu the Bionic Hamster are captured by George and Harold's evil-twin look-alikes. Now George and Harold must face their greatest foes yet: THEMSELVES! Can they handle this mess on their own, or will they need Captain Underpants to swoop in and save the day?