Koopa 3 (クッパ3, Kuppa 3) is one of Bowser's alter-egos that appears in Super Mario-kun. He represents the Bowser from Super Mario Bros. 3, not only by the "3" in his name and on his belly, but also by the cape Bowser wears in the Japanese box art of Super Mario Bros. 3. The character was created as a way to please the readers that were not able to see the continuation and conclusion of the Super Mario Bros. 3 manga, due to the publisher, Wanpaku Comic, going out of business.
Koopa 3 and his army (also from Super Mario Bros. 3) take over the Star World power-up factory, kidnap all of the stars (but one of them, Sutakichi, manages to escape), and cover the factory with a giant shell so Mario cannot be provided with power-ups. When Sutakichi comes back with Mario, Luigi, and Yoshi, they rescue the stars and Koopa 3 appears on top of the shell-dome. After presenting himself, Koopa 3 unleashes the Koopa Troop on the heroes, who manage to deal with them. Koopa 3 then jumps into battle and gets the upper hand, but his finishing blow is stopped by the traveling pod of the Star World Yoshis, who just returned from a vacation. The Yoshis pass Mario a bag full of power-ups, but before he can grab it, Koopa 3 punches the bag away so hard that it catches fire. Mario grabs it and the impact turns him into Super Power-Up Mario, who defeats Koopa 3 with a powerful blow.