Mushroom Planet

It's established in canon that Super Mario exists in the same world as the Kirby universe when Kirby comments in Meta Knight Story that if they cannot defeat Dynablaze, they can just call Mario to come save them. Gooey retorts that they can't because he lives on Mushroom Planet, which is established to be far enough away from Popstar at least that cell phones won't reach between them. Mario or this planet are never mentioned again.