Something crazier:

One must travel to ancient past of Carrotus to enter hell because in its young age, the planet has a gaping, easily accessible portal to it. The in-game jungle levels are so dangerous because they're in close proximity of the portal and evil is leaking out (as indicated by creepy eyes in walls).

Also:

Devan was given the ability to transform into a demon by Bubba, the penultimate boss, for creepy reasons.

Bolly is an abandoned, unmanned model of the very first boss in JJ1.

Chuck is a one-of-a-kind hip-hop, and a hero amongst his race, for his ability to defeat enemies bare-hands... I mean, bare-wings.

The Flashbacks (JJ2) episode takes place at the exact same time as the Turtle Terror (JJ1) episode. You never meet younger Jazz because they're in different locations of the planets (hence the visual difference).

Psych isn't a time period, but a dimension between times. The long-unavailable Rotate background was to emphasize this.

There is a stable timeloop created by the events of JJ2. Because Devan went back in time and attacked Carrotus centuries ago, the Galactic Rabbits fought an uneven battle (well, uneven if it weren't for Jazz & Spaz) and their civilization's advancement was slowed. They did, however, advance unnaturally in militaristic fields. This is why in Jazz's time, royalty lives in an old-fashioned castle surrounded by far-reaching fields untainted with urbanization, BUT at the same time they have weapons compatible with Turtles' ammunition. Devan himself unknowingly made his nemesis a threat.

I had more but that's all I can remember right now.