The Mushroom People are, as their name implies, people that are mushrooms. This race is first introduced in "Memories of Boom Boom Mountain," when the Mushroom Creatures ask for Finn's help in making music. They later appear in "The Pods" when the Mushroom Village in which they live is attacked by the Baby Pigs. The pigs used magic wands that caused the Mushroom People to turn many different colors, which they seemingly did not like. The glitter from the wands also caused them to dance uncontrollably, like it did to Jake. The Mushroom People thank Finn and Jake for saving their village, then watch as Jake cleans up their town by devouring the ice cream that covered it. Finn explains to them that "Jake just really likes ice cream."
In the Adventure Time game Legends of Ooo, Mushroom Village appears in the background. When you click to go there you hear Finn say "Jake, that village is under attack," but Jake says that they do not have enough time to deal with that.