Pilkey uses comic book features throughout his series to bring George and Harold’s comic book hero Captain Underpants to life. The illustrations rely on many components usually employed in comic books, rather than illustrated children’s books. These include panels, or frames in multiple-panel sequences to convey action; as well as splash panels, or large panels which take up an entire page; or double-page spreads to draw attention to an important event, moment, or action. Pilkey includes a flip-o-rama section in the story, where one flips pages so that the illustrations seem animated, as onomatopoeia (such as “KA-BOOM”).

Pilkey refers to and satirizes many of the tropes typical of comic book heroes and villains. Captain Underpants’s signature underpants are a humorous reference to the costumes of many well-known comic book heroes, such as Superman or Batman, who wear colored “underpants” usually over tights. Similarly, Doctor Diaper’s maniacal and sinister manner, and his plans for anarchy and destruction, are recognizable in many comic book villains, such as Batman’s Joker or Penguin.

This signature style persists throughout Pilkey’s series and is incorporated in other Captain Underpants spin-offs.