Mount Jollywood is a typical mountain. It's quite tall and rocky and gets covered in snow during winter. Notably, it's the home of Jollywood Joe the Spring Chicken.
In the series
It first appeared in "The Long, Long Winter". In that episode, Hildy and Grim held Jollywood Joe captive at Mount Jollywood – frozen inside an ice block – ensuring that spring will never arrive in Jollywood. The 7D arrive at Mount Jollywood to rescue Joe and save Jollywood from an eternal winter.
The mountain reappears again in "Uncle Humidor", where the titular character, the 7D, Queen Delightful, and Lord Starchbottom to document the Shiffle-Nosed Nergandingslinger who they make an appearance every ten years for his book. The base of Mount Jollywood also serves as a bathing spot for the colorful birds.
In "The Rock of Sages", the Glooms magically transform Mount Jollywood into a volcano. Hildy tells Queen Delightful that if she wants to stop the eruption that threatens the existence of Jollywood, she must crown her queen. Even though Delightful leaves her throne, the Glooms have no idea how. The 7D then search for gems that make up the Rock of Sages to reverse Mount Jollywood's physical appearance to end the threat. However, when Lord Grudgemunger has his hands on the gem, he grabs all magic everywhere and created a monster out of the volcano.