Mystery Dungeon is a skin created by Patty Sponge. It was requested by RDSP when they used King Neptune for a Day. The skin was released on October 6, 2018. It was made purchasable on the store for everyone, on May 19, 2019 with the release of Sponge 13. It was removed from the store and permanently retired on April 8th, 2023 with the release of Seahorse 15.
- It is the eleventh skin in SBC history to be requested from King Neptune for a Day. The first was Gravity Falls, the second was Omair Community, the third was Member Berries, the fourth was Haus of Squilliam, the fifth was Infinity War, the sixth was OBC, the seventh was V11 Rose, the eighth was JigglyTown, the ninth was Intergalactic, and the tenth was The Gay Brothers Community.