Come to think of it, who was King Koopa prior to Bowser? The earliest we see is when Bowser is a baby, with Kamek, a sort of vizier, standing in for him until he comes of age. Kind of like how there's no obvious monarch to the Mushroom Kingdom. Peach is a princess, and Toadsworth is like head of parliment or something. I guess it could be the Mushroom Principality.
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