Kirby 3DS

[TomGuycott]

Dark Matter DID have TWO very debatable appearances non-Dreamland style games (Aside from its appearance in the Kirby RPG minigame in Mass Attack). The first is the Dark Mind in Amazing Mirror, which first takes a form that is like a Mirror World version of The Nightmare, but the second form is like a Mirror World version of 0, only instead of white and red he is made of fire.

The second is even more debatable than the first. In Squeak Squad, the final boss is called Dark Nebula, and is a black star with a pink eyeball. In Japan it was apparently called Nebula Zero.

Both of these examples are VERY vague, though, and Dark Matter as he is most commonly imagined has not been present in the main gameplay outside the Dreamland series.