The Slime Kingdom is an underground state located in the Land of Ooo. The kingdom is ruled by Slime Princess and is inhabited by the Slime People. It first appears in "Love Games" during the power struggle between the kingdom's royal family. The Slime Kingdom is apparently well known for its disco, the only triple-cray rated one in Ooo.
The Slime Kingdom is located beneath the Bad Lands. The entrance to the kingdom is a bubbling slime pit in the middle of the desert. The kingdom itself is a system of yellow-green caverns covered with round, green formations. In addition, there are several bodies of slime and large amounts of prewar trash throughout the kingdom.
Like most post-war kingdoms in Ooo, the Slime Kingdom is a principality that is ruled by a princess. However, the rule of the kingdom can easily shift to other members of the royal family. This occurs if a family member gets married while the current monarch is single. This nearly occurs in "Love Games," where Slime Princess's sister, Blargetha, marries Guillermo and threatens to take control of the Slime Kingdom.
Although the kingdom's official ruler is the monarch, the Slime Kingdom also has an elder that oversees important events in the kingdom and has the authority to transfer the monarch's powers to other members of the royal family. The only known elder is Elder Plops, and he was responsible for determining the new ruler of the Slime Kingdom in "Love Games."
Despite its peaceful inhabitants, the Slime Kingdom is capable of rapid militarization and can deploy weapons such as tanks. In "Love Games," Slime Princess claims that the kingdom has the potential to defeat its neighbors, such as the Candy Kingdom, and conquer the entire world.