Dr. Diaper

Dr. Diaper (Dr nappy in the UK)is an evil scientist and the main antagonist of the Adventures of Captain Underpants.

Adventures of Captain Underpants
Dr. Diaper is the main antagonist of the first book. After his robot henchmen steal a giant jewel along with Captain Underpants, Dr. Diaper has the hero tied up and puts the jewel into his new invention. The device is designed to create a beam to destroy the moon, and the rubble will destroy the major cities of the world, allowing Dr. Diaper to control the ruins. George and Harold trick Dr. Diaper with a fake dog turd, and while he changes his diaper, they destroy his robots and activate the self destruct mode on his device. Captain Underpants uses his pair of underwater to blindfold Dr. Diaper, and all four escape before the machine explodes. Dr. Diaper is taped to a flagpole in front of the police station with a sign saying "Arrest Me!"

Perilous Plot of Professor Pooypants
Dr. Diaper is seen in the Piqua Jail laughing at Tippy Tinkletrousers.