Dr. Sporis von Fungenstein
From the Super Mario Wiki, the Mario encyclopedia
Dr. Sporis von Fungenstein is a Goomba mad scientist and the primary antagonist of the book Doors to Doom. He builds a device that creates doors from one world to another and plans to take over the world (and become indecently rich) by turning the inhabitants of the Mushroom Kingdom and Koopa clan into mushroom and turtle soup in a chain of fast food restaurants. He supposedly disposes of everyone who could have stopped him except Mario and Luigi, whom he traps in a series of worlds based on some of their earliest game appearances.
In reality, von Fungenstein works for the Royal Academy of Mushroom Science and is not a villain at all. Every few years, the RAMS gives out an award for outstanding heroism, bravery, ingenuity, moral character, and overall good looks, and he engineers the adventure to test the Mario Brothers' worthiness to receive it.