Principal Krupp once again turns into the superhero Captain Underpants in order to save the world, and Jerome Horwitz Elementary School, from the evil talking toilets and the Turbo Toilet 2000.
Seventh-grader Zoe, who comes from a big family where she's never had anything all to herself, desperately wants CJ for a best friend, but when CJ reveals that she likes the boy Zoe likes, she must make a choice.
Fifth-grader Nora Rowley has always hidden the fact that she is a genius from everyone because all she wants is to be normal, but when she comes up with a plan to prove that grades are not important, things begin to get out of control.
When he decides to turn his fifth grade teacher's love of the dictionary around on her, Nick Allen invents a new word and begins a chain of events that quickly moves beyond his control.
