MJ's name might be a reference to the deceased legendary pop star Michael Jackson, whose name was commonly shortened as MJ. It may also be a reference to one of the Insomniac employees working on the game, who was nicknamed MJ. Furthermore, one of the dogs is called Allgeier, after the Insomniac designer Brian Allgeier.
This level was originally called Catacomb Caverns.
In the PAL and non-greatest hits versions of the game, the realm shares its theme with Cloud Spires.
Sometimes, the Scarab Beetles will walk in thin air, as if there is a platform there.
There is a reference to Crash Bandicoot in this level. When one of the dogs asks you a riddle, one of the answers you can give is "bandicoot."