If you haven't checked the last update, go do it now.
Based on what was said and what was shown in the "This World" update, I'm assuming the story of Brawl.
In that would, mario and the others are forced to fight everyday, and be turned into trophies when they're done. One day, Mario got had enough of this. Mario wanted something else in life. He broke the rules by stopping Kirby from being turned back into a trophie, and together, they took a stand against the "Thing", which is the dictator of that world.
Just an idea-Metaknight works for the dictator
Feel free to say what you think the story is and your views on it