Kerma first appeared in the series as an ambassador of his people, who came to Earth to ask "typical" earthlings for help. A giant evil dragon named Herman the Horrible was trying to occupy the capital of Shell-Ri-La, and seize the gold manufacturing machines of the Turtleoids who needed them to produce energy that powered themselves. In order to bring his people to safety from Herman, Kerma conceived to introduce a plan to the High Council of the Turtleoids to relocate the entire population of his planet to Earth, and therefore Kerma went in a cloaked spaceship to Earth.
After some unsuccessful attempts to make contact with earthlings (mainly because he had no idea of how "typical" earthlings looked) - in which he also inadvertently caused the mutation of Dirtbag and Groundchuck - he brought the Ninja Turtles to his planet because he liked their honest faces. The Turtles, however, managed to beat Herman and simultaneously cause the High Council to refrain from his plan. In turn, Kerma helped the Turtles, to thwart a plan by Shredder and Krang, to conquer New York, with a new Technodrome, and left Earth as a friend and an ally of the Turtles.
Kerma later returned to Earth to ask the Turtles for help because he was a peace-loving Turtleoid, and because of their valor and their ingenuity in the encounter of danger. The first time it happened, when the police robot Destructor X chased him due to an electronic error that confused him with a criminal. Between these two events Kerma gradually realized that Shell-Ri-La would finally have to find a way to fend off such threats under its own power. So Kerma built four robots modeled after the Turtles to help defend the Turtleoids. The second time he returned to Earth when the robots weren't functioning properly. Kerma was kidnapped when Captain Dread, Ground Chuck and Dirtbag raided Shell-Ri-La to steal the gold producing machine. When confronted by Dread it finally happened that Kerma found the necessary courage, to escape and personally assist his friends in combat. He also helped the Turtles stop Shredder and Krang's latest plan. After the completion of that adventure, he returned with his new-found self-confidence to his home to teach his people to defend themselves.