The Rat King makes his first appearance in Tales of the Teenage Mutant Ninja Turtles #4 as the story's antagonist. After residing in a swamp for several months, the Rat King (who remains unnamed until the end of the issue) decides to venture into a nearby abandoned industrial park and use it as shelter against the oncoming winter. There, the Rat King happens upon the Teenage Mutant Ninja Turtles and their friend Casey Jones, who had come to the industrial park to train. Believing the Turtles and Casey to be other "monsters" who wish to take his territory, the Rat King proceeds to stalk them throughout the park, even capturing Michaelangelo and leaving him to be devoured by the rats (Michelangelo later escapes). The Rat King is eventually defeated by Leonardo who, in a duel with the Rat Kin