Oh, okay. That's cool. I'm not sure if we can take that "Earth" thing to seriously... it depends. Take OUR use of the word Earth:
Earth (note capital): planet earth.
earth (note lowercase): soil, ground, rock, ect.
Based on Kooper's comment, though, it would imply that he is talking about planet earth... but that's getting picky.
Now, about dimentions: we need someone who's played Super Paper Mario here. It's always been my opinion that just because something is in a separate dimention does not always mean that it's a different planet. Think about time (I believe it's often referred to as the fourth dimention): this planet is (I hope) the same one I was on when I started this thread yesterday... so I think what I'm saying is that's it's possible for there to be two different worlds located in different dimentions at the same inter-dimentional co-ordinates... that make any sense? What I'm thinking is this:
Say I build a massive inter-dimentional portal... let's say a door. I would argue that walking through that door would change my dimention but not my planet... necesarily... does that make any sense at all? Oh, who knows. It's so philisophical...
Okay, Mario is Missing: I think we should definately take the events of the game as canon, but maybe chalk up that comment to the lack of knowledge at where ever it was published. I mean, they saw the TV shows, probably. Maybe the English translator(s) just made a mistake? Or was that an English only game? Anyway, who knows? Nintendo Power probably shouldn't be considered (remember that Super Mario RPG guide? messed up!) as a definer, but they ARE Nintendo. Still, discounting ANY source gets me jittery, so there you go.
Until Super Mario Galaxy, then, I'd say we should just leave well enough alone... but I do think that the term Mushroom World works too... that's what I always use, anyway. Yeah, I know it's the name of the areas in Super Mario Bros. 3, but consider this:
1. The game was released early in the series. Therefore, the term Mushroom World may have been used to refer to the world overall.
2. Check out that name... WORLD... I dunno. But then you get into all those crazy "worlds" in Super Mario Bros. 1, 2, 3, SM World, Yoshi's Island, etc., etc., etc. all the way to DS.
Now, as a final musing... who are we to say that the TV series' and the Movie contradict? The movie, yeah, obviously it does, but who knows? Maybe the Bros. spent a while in Brooklyn?