Several famous Nintendo characters were considered for inclusion in the game, but ultimately dropped to focus on the game's own world and its characters, "rather than simply borrow from existing Nintendo IP."

Princess Peach was considered for an opponent, but ultimately the developers felt that punching a woman out would be inappropriate for the game. Mario did not reprise his role as the referee, or appear as an opponent, because the developers didn't think he would fit well with the game's art style.