King Kai, known as 界王 (Kaiō) in Japanese, is a wise and jovial deity in the Dragon Ball Z series. He serves as one of the four Kai who oversee the universe's cardinal directions, specifically the North Galaxy. King Kai trains notable characters like Goku, teaching him advanced techniques such as the Spirit Bomb and Kaio-ken. His planet is small and features high gravity, which is used for intense training. King Kai also provides comic relief with his love for bad jokes.