The Slaying Mantis is a giant robotic praying mantis created by Willem Viceroy. Its first and only appearance was in "Monster Drill". Hannibal McFist tried to control this contraption on his own, considering Viceroy was taking his vacation at that time. However, upon realizing he could not control it on his own, he gave Viceroy some extra vacation time if he would help him control the Slaying Mantis correctly. When it first appeared at the school, the students thought it was the practice monster, but soon realized it was a real robot intent on destroying the school. Fortunately for the students (and unfortunately for McFist and Viceroy), the Slaying Mantis was no match for Randy's Ninja Air Fist. The Slaying Mantis was later taken to Scrap City.