The author answers questions from kids:
"I got the idea [for Captain Underpants] when I was a second grader at St. John's Lutheran School in Elyria, Ohio. My teacher used the word 'underpants' in class one day and everyone started laughing. She got mad and told us that underwear was not funny. We all laughed harder. Usually, when the class cracked up, it was because of something I had said or done. But our teacher had never made everybody laugh so hard before. I realized then that the word 'underpants' was a very funny word."
Read the whole interview.