Mt. Fondoom is a volcano in Marzipan City. Fondoom's lava is made of fondue, and the King of the Sky sometimes visit the volcano. Fondoom also made its first appearance in "Burple Nurples," when Mung threw the poisoned nurples to the crater, making the volcano erupt.
- Mt. Fondoom is likely the only volcano in Marzipan City.
- The Burple Nurples caused the volcano to erupt.
- The mountain is a reference to the Lord of the Rings' Mt. Doom.
- The name of the mountain was only said once by Mung.
- The sign of the mountain was not seen again when Mung and Chowder are climbing down the same way they came.