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Perhaps it has something to do with the time-space continueum or a paradox. Like in Back to the Future when Marty travels backwards in time, then forwards to the present, the old and new Marties are both there. Maybe if Mario went back in time, then forward again to date his new Mario Golf games, etc., maybe his past and future self were present in Mario Golf. But I've always wondered, wouldn't the past Mario go back in time again eventually, dissappear, and reappear? Then the number of Marios would multiply each time. Thus, the present Mario(the one that time-travelled originally) would have no control over the past Mario(s), and I should think that eventually there would be a paradox, because even going back in time once could have a severe effect.
Well, I tried to explain it, anyway. :)
-YOSHI :P