Okay kiddo, do you know what an aristocracy is? It means a group of really important people who have a lot of power and money. Now, have you ever heard of a bunyip? It's a mythical creature from Australian folklore which people believe lives near water bodies.
So, the Bunyip Aristocracy is a made-up term to describe a fictional group of really important mythical creatures, the bunyips, who have all the power and influence in their world.
Think of it like a group of kings and queens but instead of being human, they are bunyips. They would be able to do whatever they wanted and make all the rules since they are in charge.
But remember, it's just a story and not real!