They originally showed up in a different game.

"Dream Factory: Doki Doki Panic", right?

Well, time went on, and eventually they arrived in mainline games too.

The settings just kind of blended together.

Not the point. What I mean is, what doesn't first appear in a mainline title

can only show up in spin-offs from then on.

...can only exist in made-up worlds.

In the same way, the stuff of picture books and dreams...

Well, the companies did collaborate, but...

"Heihou" means "squared"... Square? Square Enix?