Multiverse

FBDJ
The FBDJ Universe is the true original universe. At this point, there was only Zack Casey living along the outskirts of what is now Catsinburg, however there was no kingdom. His neighbor was simply named John, living in a housing development. Zack was blue a fox that aspired to be a DJ, known as the Furry Blue DJ. Later timelines introduced a proto version of Saveli Cornell and his android assistant as an early antagonist whom was more a parody of comic villains at that time.

Proto
The Proto Universe was the first to carry the Casey Universe title, but there was no kingdom and Zack Casey now lived alone in what is now Furtropolis until he met Aidan Cheddar.

Furtropolis was one of many small city-states out in the middle of a barren desert. It had giant, tall and thick walls in order to block any dust storms and protect against any attacks. The Central Tower had Grand Central Terminal beneath it in order to save on space and provided extra stability for the tower above. Mice lived under and helped maintained the subway network below.

Saveli Cornell would go to overthrow Furtropolis which started a civil war. Zack Casey and Aidan Cheddar would try to defeat him the first time around but were instantly kicked out. They try again by traveling the continent, where they met Kit Welsh whom teamed up with them, and oceans for a year until they could come back around through the docks, ready and prepared.

Bark Pack
A re-imagining of both the FBDJ and Proto Universes that merged them together. It kept Furtropolis while keeping the main characters along the outskirts. Main locations varied from a small town to a university. Meanwhile, Bark Pack threw out the Savelli Cornell plot and focused on slice-of-life.

However, later iterations would introduce a new villain, Silverclaw, and begin experimenting with more fantastical elements with the Odium crystals, inspired by the Infinity Stones, that Silverclaw wants. Bark Pack also introduced Felix and Tom, both university students. Felix's family owned the university but didn't like that fact and hated being the center of attention. Meanwhile, Tom was a average student dealing with the social troubles of being a kipomito - they were only recently introduced in later iterations of Bark Pack.