Morty Fyde was the Jerome Horwitz Elementary School science teacher. He is not mean and rather dorky; his name is a pun on the word "mystified" while his full name is a pun on the word "mortified".
Captain Underpants and the Invasion of the Incredibly Naughty Cafeteria Ladies from Outer Space(and the Subsequent Assault of the Equally Evil Lunchroom Zombie Nerds)
Mr. Fyde is having class with George and Harold and they start making cat and dog noises without moving their lips or opening their mouths. He thinks that he's going crazy and countines on with class, much to the students' dismay. He showed the class a fake volcano, which gave George and Harold the idea to prank The Lunch Ladies. After a couple of animals noises, he left to go see a doctor as he thought he had gotten nuts from hearing things.
Captain Underpants and the Perilous Plot of Professor Poopypants
Mr. Fyde quits because he dreamed that he had been eaten by a talking toilet, thought he heard cats and dogs meowing and growling in his classroom, imagined that the school got flooded with sticky green goop, and he thought he saw a group of abominable snowmen chasing George and Harold down the hallway. When Mr. Krupp tried to tell him that can all be explained as George and Harold's doings, Mr. Fyde stated that he saw a big fat bald guy in his underwear fly out the window (the big fat bald guy obviously being Captain Underpants). As Mr. Krupp could not find that as their doing, Mr. Fyde retired to leave the school for the greener pastures of the "Piqua Valley Home for the Reality Challenged" and was eventually replaced by Professor Poopypants.
Captain Underpants and Terrifying Re-turn of Tippy Tinkletrousers
Mr. Fyde makes a very brief appearance in this novel, as this story is set four years in the past from the previous books and Mr. Fyde is still the science teacher at Jerome Horwitz Elementary School. He is seen in a teacher's meeting along with Mr. Krupp and Ms. Ribble.