When Professor Pippy P. Poopypants comes to Jerome Horwitz Elementary School to teach science, and he goes off the deep end because students make fun of his name, only Captain Underpants can save the school from the professor's perilous plot.

The monstrous Turbo Toilet 2000 is determined to take revenge on George, Harold, and Captain Underpants.

"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...

Only Captain Underpants can stop the three evil space aliens who have invaded Jerome Horwitz Elementary School and turned everyone into lunchroom zombie nerds.

The Notebook of Doom is missing and Alexander and his fellow monster-hunters Rip and Nikki are convinced that the boss-monster has it. But is that monster the mysterious Principal Vanderpants--who is certainly behaving oddly--or someone else? They need to figure that out quickly because a mistake could have deadly consequences for Stermont Elementary.

Owen and his friends decide that spying on the school principal at his own house will be a fun challenge.

When she is named Principal for the Day, Frannie wonders if principals assign their own punishment when they get in trouble for using office supplies or accidentally set off the fire alarm.

While Raven is away, Luca breaks his promise to her and returns to the Wish Library, asking to be in charge at school, but being principal for a day is not all fun and games.

Tired of following the strict rules of their grumpy replacement principal, second grader A.J. and his classmates try to find a way to bring back eccentric but lovable Principal Klutz, who was fired for bringing a wild turkey to the school's Thanksgiving Day assembly.

When the new vice principal is put in charge of Ella Mentry School for a few days, she tries out some very unusual ideas about how students learn.