The final boss was the biggest object of them all. Consisting of forehead, head, left wing, right wing. Each individually hittable/destructable with two stages. Most bosses are split into several parts so that they can be animated and destroyed in several stages.
All enemies and also some other objects from the overworld. Most of these also appear in the other worlds.
This world used palette switching for the copper wired backgrounds. While playing the game you can notice that the copper wires are never on screen at the same time as the brown organic wires, because they both use the same color registers. The game can only change these unnoticed when they are off-screen.