Very strong visuals, music, and SFX. The pixel art in particular is fantastic and fluid. The whole game has an incredible style. I'll echo what others have said that this looks like a finished product that took months rather than weeks. The game feels pretty good to play, no issues with the controls, but I think it's simultaneously very easy and very punishing. I don't consider the game being easy a bad thing, I prefer it as someone who played all of the other hard IWBTG-style games in the jam, but the game has a few aspects that can cause things to snowball into being pretty frustrating.
As is, the fatal flaw of this game is the Yoshi's Island wig recovery mechanic. It's a cool idea, and most of my problems with it come from the spotlight effect that significantly reduces the player's vision, but I think some design quirks get turned into real problems because of how the wig recovery works.
I'll start with the spotlight effect. When you take damage and lose your wig, you're probably in a situation where you're likely to take damage again, so reducing what the player can see while they're in a dangerous situation obviously makes it more likely that they'll be hit again. It's especially frustrating when this happens from something you can't see, and it kinda feels like the game kicking you while you're down. On one hand, that can be a skill issue, because you could argue that players should be able to remember their immediate surroundings when they get hit. However, in the final boss fight, if the player loses their wig and the screen goes dark, they can't always see things like random enemy spawns or the final boss's visual cues. The wig has a tendency to fly to either edge of the arena, so if you're following it you can't see the center where the boss is, or you may need to move from one side to the other where an enemy you didn't know spawned is waiting for you. This leads to cheap deaths, and since dying in this game means being sent back a level, it often feels like you lose progress from things that feel like they aren't your fault, because you can't react to things if you don't know they're happening.
Enemy health scaling is largely pointless in this game, with two exceptions. The first one is the egg enemy, which actually has a sense of self-preservation and will try to run, which I actually like, because it makes sense conceptually and makes the enemy unique. The second one is when you've lost your wig, and this is when the scaling can become a problem. In later levels, it can take 10 seconds, maybe longer, to fully defeat an enemy with how high their health is. So when you lose your wig, it typically isn't worth it to try and defeat whatever dealt the initial damage, because it will run out your wig recovery timer, you'll waste your damage i-frames, and the longer you wait the further away the wig can travel. So usually the initial threat is still there and can finish the job while you scramble for the wig. And, of course, the spotlight visibility issues are still present, so if this happens in a room with 3-4 enemy spawns, or if you need to follow the wig into uncharted territory, taking damage can quickly snowball into a death.
Despite those gamer rage paragraphs, I do think the game is easy. Outside of the egg, every normal enemy gets stunned on hit or is immobile, so once you get an initial bounce on them you can just keep bouncing on it crazy style until it dies. As health scales, the only thing that changes is how long I have to wait in one spot before moving on. I didn't use the punch much. Generally, enemies are pretty easy to draw aggro and pick off one by one as well, although this slows things down even more. That said, this is only really a problem when replaying levels or in the final floors.
It took me about 6 tries to beat the final boss, and I only died 3-4 times in normal levels, and some of those were because I was tilted from dying on the boss. I do think I got lucky on the winning final boss attempt. I didn't do it hitless, the wig just cooperated when I lost it. About half of the boss attempts died to the visibility problems I've yapped on about, but I wouldn't say any of the boss's attacks feel too unfair when you can see them coming (at least, with the double jump wig). The sound cues and boss dialogue were pretty funny, by the way, and it has some of the best pixel art in game, and probably the jam.
There's some other problems with the wig recovery. I only had it happen once, but I lost the wig on the stairs leading down in the room with the Mario pixel art head, and the wig moved right while keeping the same altitude, so it was impossible to get it again because it wouldn't come back down within the time limit. I'm unsure if that can happen in other rooms with lots of vertical space, but I'm assuming it can. I also had 2-3 instances where I lost the wig, then got the wig back while I'm guessing I was overlapping an enemy or fire with my no wig i-frames, got the wig back, then immediately lost it again instead of getting the i-frames upon wig pickup. That I could see being intentional, but it doesn't feel good.
A lot of this could be fixed if you just add transparency to the spotlight effect, so you can keep the effect but still see things underneath the black space. Maybe add a way to enforce separate maximum vertical and horizontal distances the wig can be from the player, where if the wig goes past one it starts moving back towards the player until it's in range. I'd add separate ones because generally it seems the game is more horizontal than it is vertical, and if you used one value for max distance it'd be easy to run into problems like the Mario room if it's too big for one axis.
With all that said, this is still undoubtedly one of my favorites from the jam. I saved this one for the end because I figured it'd be quality. I'm glad to see another FCK game after last year's, and this one was definitely better. Great work!