I may be nitpicking a little, but...
"Mario had entered it" would make it more clear that some action happened after the previous one.
"She asked Mario" would sound more correct.
"and Bowser had been there" also would make more clear that Bowser was on the island before Mario.
The only serious complaint I have is that most levels, particularly in worlds 2-4 and 7, feel the same not only due to their aesthetics, but also usage of monsters in general. This makes the hack more boring to play and - in order to prevent that - use more distinctive aesthetics and more variety of monsters for them.
This hack seems promising by far and I wouldn't like it to get hated for such a thing.
I have a Discord server as well!
Der ver zwei peanuts, valking down der Straße, und von vas assaulted...peanut. Ohohohoho!