Frog King is a spirit animal that lives in Mr. Slave's digestive system along with two other spirit animals, Sparrow Prince and Catatafish. He helps Lemmiwinks get out of Mr. Slave's body at the end by escaping through his mouth.
In "Bass to Mouth", the Frog King appeared to Lemmiwinks to warn the rodent that his brother Wikileaks' mischief at South Park Elementary. He trains Lemmiwinks to fight his evil gossiping brother and leads the children to the fight between the two rats.
The Frog King wears a king's crown, unisex robe, and carrying a royal scepter.