Glooble eggs only exist as a result of leftover slime and egg shells from Muckles. Due to the large amounts of nutrition that still exist in Muckle eggs after hatching, the fungus that accumulates eventually causes the broken egg to reseal itself and cause a new creature, the Glooble, to begin to grow. These eggs thrive solely from the nutrition left behind by the Muckle, so they are able to survive outside of Ark City's sewer systems with relative ease.
Despite their close relation to the Muckle, if a Glooble egg is raised outside of the sewers, it is likely that it will hatch to be completely odorless. While they hatch from the same eggs as Muckles, their bodies' textures are noticeably different. The Muckle is made up of slime that will absorb things that it touches. Gloobles, on the other hand, have bodies that are very similar to jello or rubber. Their skin is very smooth and difficult to penetrate.
Gloobles seem to be very inconsistent. Gloobles have personalities ranging all over the spectrum, and their general behaviors are very different from one another. Studies on their DNA strands have also shown major inconsistencies within the species -- the only thing that they all share is their appearance and body structure. It is currently unknown why all Gloobles seem to behave in different manners.