Bowser Jr. is the secondary antagonist of the Mario franchise. He is also one of the sons of Bowser himself. He made his debut appearance in Super Mario Sunshine as the main antagonist. He looks just like Bowser, except younger and he constantly wears a bib with fangs drawn on it perhaps to look more intimidating. He seems to be the direct superior to the Koopalings, even though they are older than him.
In the Legacy of Chris Thorndyke, he and his siblings betrayed their father, because he described that he was as pure evil, because of the Dark Star and his megalomania increased in a higher rate as conquering the Mushroom Kingdom with an iron fist, so that he had joined Mario against the war against his evil father.
He is voiced by Scott Menville in the English dub and he will be voiced by Tetsuya Kakihara in the Japanese dub.