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According to Luigi in Paper Mario: The Thousand-Year Door, the Chestnut King is the villain who kidnaps Princess Eclair from the Waffle Kingdom and brings her to Hatesong Tower. Luigi travels to the tower by using the Marvelous Compass. Once there, Luigi challenges the Chestnut King to an epic battle. The king, dripping with toxic goo, eventually loses to Luigi and his Hammer. However, before Luigi can deliver the final blow, Princess Eclair appears and stops him. As it turns out, the Chestnut King and the princess are actually lovers (much to Luigi's dismay). The King was transformed into a monster through the magic of Minister Crepe of the Waffle Kingdom. Eventually, Luigi defeats the shadowy Crepe, presumably restoring the Chestnut King to his former self. Luigi never admits that he was wrong in believing that the Chestnut King was the Princess's captor, and Mario can only read about it in the Super Luigi book series.
The character Goomboss, also known as the Goomba King, shares the same name as the Chestnut King in various European translations and the original Japanese version of the game. Goombas are known as kuribō, "Chestnut People" in Japan, which is where Goomboss' name is derived, whereas the Chestnut King may be following the convention of food-related Waffle Kingdom names. It is unknown if they are meant to be the same character, as Goomboss was never said to be a transformed monster and has appeared since Paper Mario: The Thousand-Year Door's release.
Names in other languages