Zorx, Klax, and Jennifer are 3 space aliens who planned to invade Piqua, Ohio from book 3. They put this into plan by infecting the school with Zombie nerd milkshake. They serve as the main antagonists of the book.
They landed on top of Jerome Horwitz Elementary School. Later, the lunch ladies at the school quit and the aliens filled in for their spot. They plotted to turn the students and faculty at the school into Evil Zombie Nerds using Evil Zombie Nerd Juice. George and Harold were eating lunch in Mr. Krupp's office and walk out and saw then problem. George and Harold snuck into the kitchen and pured the Super Evil Rapid Growth Juice outside. They told Mr. Krupp out the situation, but he didn't believe him. Ms. Anthrope walked into his office and took a huge bite out of his desk. George, Harold and Mr. Krupp went into the kitchen and one of the aliens snapped his tentacle and Mr. Krupp turned into Captain Underpants. The heroes were trapped by the Zombie nerds and they climbed up a ladder to the roof. They went into the alien spaceship. and saw a refrigerator of juices. They were jailed in the spaceship by the aliens. George and Harold switched the Super Evil Rapid Growth Juice label with the Ultra-Nasty Self-Destruct Juice label. Then they would give them Super Evil Rapid Growth Juice to enlarge them. They were killed when Ultra-Nasty Self-Destruct Juice was poured in the engines.
- 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).