These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Batman Gambit: Fanon says this Wario's master plan is this: hire Tatanga to kidnap Daisy. And when Mario goes to Sarasaland to save her, enter Mario's castle and take over his country.
The instruction manual for "Six Golden Coins" does indeed say that Wario took over Mario Land during the events of the first game. Take that how you will.
It's Short, so It Sucks : 12 levels. Can be easily beaten in under an hour, albeit not on the first try.
Nightmare Fuel: The way the enemies die in this game is actually kind of creepy. Unlike the NES Mario games, where enemies generally flip upside-down and fall off the screen when you jump on them, here they lay on the ground, flattened and dead for a few seconds, before flopping off the screen. It gets worse with the Koopa Trooper analogues, which explode when they die.