|The following information is from the Adventure Time comic book series.|
It may not be part of the same canon or continuity as the animated series.
Lumpy Space Predators are animals who live in Lumpy Space. One of them, a Lumpy Space Rat, attacked a group of Breakfast Organisms when Lumpy Space Princess brought them to Lumpy Space while their home was growing back. There are presumably more varieties besides the Lumpy Space Rat.