It originated from this old comic idea I had in where the main character is dreaming about his childhood, but he isn't aware that he's dreaming(I didn't write whether or not he was sleeping, in coma or really dead). It's like he can remember his adulthood, but only in bits and pieces. The problem I encountered was the inhabitants. Like childhood friends becoming reoccurring characters. Since the events in the dreams didn't happen in the real world(or "wake up" world), I didn't want the dream residents to be mixed up with the wake up residents. Then I wanted the idea to work for everyone that exists in the "wake-up" world, since I didn't find it fair that the only the main character had such an thing.
From there I thought about out own universe. Like we being on planet with almost no way to see what's beyond it. I though it would have been cool if dreams worked the same way. It's a realm where anything can happen for any individual, but it doesn't mesh or mix in with different people since everyone has thier own separate planet. Then I worte some terminolgies so things are organized.
-Dream Planet: (you know what it is now)
-Dreamer: Basically the creator of the planet, even though some Dreamers end up being "born" in separate locations.
-Wake up world: Basically the Dreamer's reality.
-Dream Residents: These are inhabitants like animals, humans or creatures that appear in dreams. Can be shaped from people the Dreamer met in the wake up world. Cannot be changed or altered.
-Nightmares: These normally show up on sections in planet. They originally collide with Dream Planets in the from of meteorites and do things to change the Dreamer's personality. There are cases in there Nightmare fully take control of the Dreamer's planet or personality in reality. Laws also inists that Nightmares are not entitled into having dreams of their own. It's a taboo that kinda pisses some of them off since Dream Residents are entitled to becoming or having Nightmares themselves.
There's a bit more, but that's the basic idea.