Mario's Castle
"Mario Land," including the castle on it, were given to Mario as a way of saying thank you, from Toadstool and/or Daisy. After he got it back from Wario, however, he realized he didn't need a whole island to rule or a big castle to live in to be happy, which is why in future games we see him living in a small house; given his blue-collar roots, he likely finds it much more comfortable.- The house on the island is too gigantic for Mario to call home either. It really gives the impression the location is part of Giant Land. Inconvenient for the brothers in the Mushroom Kingdom to commute back and forth to daily.
- Perhaps that's why we don't see Wario's castle after Wario World. Wario only wanted a castle bigger than Mario's to make him jealous, and once Mario traded in his castle for a modest house in the Mushroom Kingdom, Wario decided there was no point to owning a castle anymore and moved to Diamond City. Or he lost his castle when he couldn't be bothered to save more than ten Spritelings and had to move anyway.
Mario Land is a theme park
Think about it: six main areas surrounding a castle in the center. Seem familiar?- Might even be the same "Mario Land" we see in the intro to Mario Party 2. Incidentally, Wario tried to seize control of that one as well.
- They even have some of the same themes: space, water, horror...
- It would explain why Mario has a "castle" in this one, but lives in a small house with his brother in all other games. It was never "his castle" to begin with, it's just the central attraction of the Mario Land Theme Park.
Mario Land is home to a giant
No coincidence the island has a massive house with a functional kitchen, a large pumpkin patch, a towering tree with its tops in the clouds, and a Mario wind-up toy. Mario Land is the residence of someone big. Very big.- Possibly a rabbit, as the Bunny Mario power-up was the gimmick of this game.
- The manuals/overworld show the hippo that helps you to Space Zone is huge, maybe he was meant to be the giant? Would explain how his bubbles are able to get Mario into outer space. But couldn't be shown in-game, due to the technical limitations of the Game Boy.
- Its Fridge Brilliance if the giant's the hippo, as the cave system to Macro Zone shrinks Mario down to bug-size. Whereas the giant would shrink down to normal size to fit inside the house.
