Mount Saint Dimmsdale is the mountain where the "Dimmsdale" sign is located.
In Balance of Flour, after Anti-Cosmo and Anti-Wanda had sucked Cosmo, Wanda, and Poof into their vacuum cleaner and were about to suck Nana Boom Boom's Fairy Cherry recipe from Timmy's brain, Jorgen poofed into the room and blasted Anti-Cosmo and Anti-Wanda into the sign, changing it to "Mildewads." Later, in Dad Overboard, when Mr. Turner was remembering his past fiasco trips, and one of them was the trip to Mt. St. Dimmsdale, where he had taken a wrong turn and drove the car into a volcano.
- The name Mount Saint Dimmsdale is a reference to Mount Saint Helens, an active volcano in Washington state that famously violently erupted.