1-1: Exercise in the Snow
Yes, World 1 will be the Ice/Sky world of this hack. So basically the level's just Yoshi cruising through the snowy mountains on Flatbed Ferry paths, while avoiding flying Bumpties, Baron Von Zeppelins, Skeleton Goonies, Gusties etc..... Heck, there's even one section which you have to avoid Fuzzies! Isn't it just plain cool to have Fuzzies in the first level of a YI hack?
1-6: Endless World Of Goonies
This level will take place in a Plains/Sky setting, and it contains all types of Goonie enemies: Goonie, Flightless Goonie, Bowling Goonie, Hefty Goonie, Skeleton Goonie and Flightless Skeleton Goonie. Besides Goonies, you will find other enemies such as Crayzee Dayzees, Koopa Paratroopas, etc...
2-1: Clawdaddy's Cove
This level will mainly focus on the Clawdaddy enemy, and since W2 will be the Jungle world, not only they will be part of the enemy list in this world. You will also come across Ukikis, Frog Pirates, Spear Guys, and Lunge Fish. The level starts in a jungle/swamp area with many Clawdaddies, Ukikis, Frog Pirates and Spear Guys (and there's a 1UP bonus area with water and a Nep-Enut traversing it) After that, you will come across a Submarine Yoshi Section with Boo Guys throwing projectiles from above water, and not only will you find a load of Clawdaddies underwater, but you'll find submarine section-only enemies such as Preying Mantas, Piscatory Petes etc..., and after that section, you will enter the final section in a sunset lake with Clawdaddies and Lunge Fish.
2-4 Fortress of the Thievish Prince
Yes, by Thievish Prince I mean Froggy. This is not a jungle/swamp-only fort, there are more types of sections to be found here. First off, we have a dark room section with many Spookies, Little Mousers and Skull Mousers, Lava Drops, Bandits and Boo Guys. Baby Mario is very likely to be stolen by most enemies in this fort! Anyways, later on we have a tower/fort section with lava, Dizzy Dandies, Solo Toadies, a Fishin' Lakitu, Grim Leechers, and more Bandits, of course. Lastly, right before the boss section, we have a jungle/swamp section with Frog Pirates (that one I'm sure you knew was coming because after all this is Prince Froggy's Fort), Clawdaddies, Ukikis, Spear Guys and Dancing Spear Guys, and a few spray fish.
And then, have fun getting Yoshi out of the malevolent Frog's insides!
That's all I'm thinking of as of right now, but don't you worry, there will be plenty more from where these came from!