Uh...the Subconians said that they were cursed, not Mario himself.
So I found the old manual for SMB2 and as it turns out, we're both right!
"Welcome to 'Subcon', the land of dreams. We have been cursed by Wart and we are completely under his evil spell. We have been awaiting your arrival. Please defeat Wart and return Subcon to its natural state. The curse Wart has put on you in the real world will not have any effect upon you here."
Not really sure what curses they are talking about since the manual doesn't explain what the curses actually are, so I just had to use my imagination there. Hmm, so maybe the "subconians" are cursed in that many of them were all turned into those flying Beezo enemies? I always thought they looked pretty similar... As for Mario, yeah I still think he was cursed with eternal sleep or something.