I'll give it a try
I feel like this should say "Mario hasn't been able to sleep for a long time now, and he finds himself in a strange, unfamiliar land..."
Unedited Yoshi's House text box, I assume you plan on doing something more with this in the future, so I'll let it slide.
Yoshi's Island 4
This level has a few problems, first of which being that this gimmick with the sticky rope should have been introduced in a safer environment, rather than just throwing this at the player.
I get what you were going for with this Wiggler, but I fell between the segments a couple times while testing, and that just feels unfair.
(I understand that you're supposed to do it all in one motion, but the point still stands that if the player doesn't do that bit in one motion, they're pretty screwed.)
Okay, that's just rude
There's no indicator that I had to spin on the bridge, and no indication that the blocks below me were going to disappear, maybe put an A above the 2nd log to indicate that the player should spin, and have some other tile indicate that the blocks will disappear.
Empty stretch before surprise Bullet Bills. Surprise deaths like this are generally bad practice, especially after a difficult section.
And a problem I have with the level overall is how you used invisible blocks on the surface of the water to simulate a pit.
If this hack takes place in a dream world, then maybe have the water be a different color and act like lava, as that would not only make dying faster, but it would also tie in to the theme of the hack.
Also, I noticed that the goal music cuts out after a few seconds.
MASSIVE Cutoff here after beating the 1st level.
If this was the intended effect, you should try making it look better, because this is just ugly.
Yellow Switch Palace
The first room in the Yellow Switch Palace is pretty hard on the eyes with this harsh palette.
I just don't understand the point of this pit, why does this need to be here? There's no way to get out, and the player just has to Start+Select to get out of it, so why is it here in the first place?
So the Yellow Switch Palace was just two corridors, a pipe, and the Switch. Given the expectations that were set with the first level, I was expecting a lot more from this level going into it. So it's just surprising seeing it have this little content.
(Also, the yellow flashes from the 1st room are gone in the Switch Room)
Why does the overworld clean itself up after the Yellow Switch Palace is cleared? Why didn't it just stay as it was the whole time?
So the only reason the Yellow Switch Palace needed to be cleared was to give access to the Secret Exit. This was all just a really roundabout way of just getting past the 1st level.
(I haven't seen if the Yellow Blocks are in any other levels, so I'll just say that you should cut the Switch Palace all together and let the player move on without needing to re-enter the level for the secret exit.)
I didn't mention it before, but I'll mention it now, why are the level names unchanged? And why do we go from Yoshi's Island 4 to Yoshi's Island 1?
Yoshi's Island 1
Cutoff issues with the Yellow Block, and the Mushroom moving through the terrain doesn't look too good.
Now I see that the Mushroom was supposed to do that so you could pick it up here, I just think that you could have made this idea look less like a side effect of poor planning and more like the intended solution.
(Maybe have the Mushroom travel down a separate corridor, so that it doesn't have to clip through terrain in order to get to where it needs to be.)
This dirt tile right here, cutoff and allows for massive amounts of cheese.
Here's a collection of images of the things that you can do (That I can only assume were unintentional) once you jump in that hole.
(Also, cutoff dirt tiles in the 4th image)
This entire ceiling is just cutoff dirt tiles.
More cutoff tiles with this slope
Here's what you could do to make this level look infinitely better, just get rid of all of the cutoff tiles. Not only would that make it look better, it would also fix some of the cheese in the beginning of the level.
#1 Iggy's Castle
Nothing indicating that I had to scroll the screen here, maybe place a sign that says R here so that the player would think to scroll the screen to the right.
The Mushroom from this block is too cumbersome to obtain without taking damage, and I assume it's necessary because you can't spin jump off of grates. I'd suggest letting the player spin jump off of grates and removing this required mushroom.
Some Slowdown with these Bowser Statues
Also, this happened after I got the Goal Orb
Yoshi's Island 2
(seriously, these levels need their own names)
Why did you have to replace the screen scrolling pipes with logs? This just makes it harder for the player to figure out what they're supposed to do.
Other than that, this level didn't really have much wrong with it.
Yoshi's Island 3
I tried moving the red block up so I could go in the pipe, but I died while I was in the pipe, and now time is frozen.
I had to reset in order to fix this. (The Screen scrolling pipes just seem to be buggy in this level overall so I'd fix that)
This clapping chuck turns into garbage tiles when he's on screen
I couldn't get past this level, so I hope everything I've said is enough.
"What's 9 + 10?"