|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.
The Breakfast Organisms are in the back-up story for the third issue of the Adventure Time comics. They are organisms made out of breakfast foods, like sausage and eggs. Lumpy Space Princess eats bacon from the bacon fields, and so Breakfast Princess chews her out revealing that the bacon fields are home to the Breakfast Organisms.
Lumpy Space Princess thinks the Breakfast Organisms are cute and feels guilty for eating their home. She brings the organisms over to Lumpy Space, where they will live until their home grows back. Once she takes them to Lumpy Space a Lumpy Space rat tries to attack one of them, so Lumpy Space Princess gives them Lumpy Space outfits to mask their scents.
The Breakfast Organisms, after adapting to their new outfits, begin to pick up the "lumpy" personality traits as well in order to survive in their new environment. Apparently after they returned to the bacon fields they reintegrated into their ecosystem well despite their new outfits.