I'm pretty sure you’ll heard of Captain Underpants, right? The series revolves around two fourth graders, George Beard and Harold Hutchins, living in Piqua, Ohio, and Captain Underpants, an aptly named superhero from one of the boys' homemade comic books, that accidentally becomes real when George and Harold hypnotize their megalomaniacal principal, Mr. Krupp. Now that we have the introductory settled, I’d like to start my theory:
Captain Underpants lives in the afterlife. The story mentions that he can quote-on-quote “fly”. Angels, or souls after they died, can fly in the afterlife. Captain Underpants is an angel. Now here comes the story behind Mr. Krupp/Captain Underpants.
In reality, Mr. Krupp is, or was, a nice guy. He had a beautiful wife, and 3 kids; all a person could ever ask for, am I right? But suddenly, he turned from a nice, caring, loyal family man to a drinking, bachelorette that didn't care when his kids were in danger or were being bullied in school. One day when his wife was driving the kids, a drunk driving accidentally crashed into them, killing his wife and kids instantly, and crushing their skulls to death. Meanwhile, Mr. Krupp learns this happened, and suddenly falls into a depression he couldn't escape.
Later, he became a principal for a certain school. One day, one of the students – who was very low functioning autistic – accidentally was pushed into on-going traffic. Mr. Krupp, being the nice guy he is, ran to the kid’s safety. But he was too late, as a speeding car crushed Mr. Krupp to death when he tried to push the kid out of the way. They both died on the spot.
Mr. Krupp however, woke up; he wasn't in the street anymore, but now a white, foggy heaven-like place. There he met God, our savour, and he gave Mr. Krupp wings – which in his eyes were superpowers. He was able to start a new life there, and so he did. He created an illusion, where he was once again a school principal but this time, Mr. Krupp started to hate kids for what they “did to him”. That’s why Mr. Krupp hates kids, he regrets helping that special needs kid and wished he had never done it.
He began to get a craving to torture kids, as if they were in Hell, and thought up George Beard and Harold Hutchins. He made them troublemakers, so it would be easy to bust them when he gets the chance. After this “new life”, he turns back into an angel and flies away. One day, he gave himself a new name: “Captain Underpants”, and started to live under 2 names for now. Then he created fictional villains to fight, like Professor PoopyPants, and so on so forth.
And that is the story of Mr. Krupp.