In the levels "Cortex Power" and "Toxic Waste", there are two enemies that appear to be genetically-altered gangster potoroos, similar to the boss character, Pinstripe Potoroo. This is unusual as no other genetically-altered animals appear as common enemies in the game.
This also implies that Dr. Cortex created a larger gang of potoroo enforcers, but because Pinstripe has rarely appeared in later installments, this has never been elaborated.