At the very beginning of the stage, have Pikarina investigate the big mushroom to get the MUSHROOM HEAD. You'll notice piles of sludge as you progress through the stage, which are marked with the bomb symbol, so that means hit it with a bomb to destroy them. The first screen is pretty straightforward and there isn't anything else hidden.
When you get to the second screen, you'll see the Kappagaeru mother going crazy and you'll automatically get the KAPPAGAERU SPROG HEAD. Once the lily pad gets close, jump onto it and then cut your way across the cattails. You'll see two Grubs here, as well as one in the background (use Pikarina to hit the boy on the right). The rest of the way to the gateway is easy.
You'll see a fish with the bomb symbol on it, so toss one in its mouth when it's open to make it spit up water that you can cut to cross. There will be another enemy here, who opens its mouth, so toss a bomb into it to get rid of it. Remove the sludge and use the spring and flower petals to continue to another fish. When you get to the big drum, use the Taiko Drum Head (if you have it) to get sent to a bonus stage.
There will be more sludge, so bomb it and use the flowers to reach the gateway. Make sure you wait for the second lily pad to move all the way to the left, jumping on it to make sure you don't sink, until you can jump onto the platform. Quickly cut your way across the cattails and if you have the Jizo Statue Head, use it on the statue to get some Moonsparkles. The rest of the way to the gateway should pose no problems.
The next screen will have a big glob of sludge here, which reveals some green webbing and two spitting fish. While you can bomb the fish, they will get stuck to the webbing and can still hurt you. There will be another part with the webbing and spitting fish after this, then you will have to be careful of the falling rock in the cave. If you have the Lantern Head on you, use its action past the enemy.
Kappagaeru Mother
The mini-boss fight with the Kappagaeru Mother is fairly easy. There are two platforms on either side, with some of the green webbing from before in the air. Kappagaeru only really has two attacks, one of which involves using her tongue from across the screen. The other has her spitting three times while moving across the screen.
To damage her, you will need to drop a bomb on her head whenever she stops, with the perfect opportunity being after she stops attacking. Once she does and you hit her with the bomb, she will be exposed for another bomb, this one actually damaging her. There's nothing new after her taking damage, so do this three times to finish the battle.
Finding the Trees
Right away, you'll be able to perform the Mushroom Head action if you have it. Continue to the right, clearing the sludge and using the spring to get above. Now, there will be spots of sludge that will continually drip from the ceiling and while you can clear the floor, it will continue dripping, so jump over when it's clear. You also have to watch out for the squirrels running around, as they can harm you.
Once you get past the two lines of dripping sludge, shake the bundles of leaves with Pikarina to make some loose leaves appear. Use these to get to the branch above, where you can hit three squirrels in the holes to get the ACORN HEAD. As you pass the two big piles of sludge, the rope beneath you will start to fall apart, so keep rolling to the right until you're safe.
For the next part, you will need to stand on the platform, then throw a bomb at the sludge. After it's gone, throw another bomb into the hole, which should roll down below and launch you to the next platform, where you will need to do the same thing. You'll eventually come to some vertically stacked mushroom springs, but there's a large hole to the right of them with a large squirrel; you can use the Acorn Head action here. Use the springs and leaves to get to the top, where you will now be fighting General Rat.
BOSS: General Rat
The battle with General Rat takes place with the two trees you need to rescue in the background, both of whom are covered with spots of sludge. Ignore Rat for now and hit the sludge pieces you can reach with bombs. Rat will be flying around and dropping pieces of sludge along the ground, which you can remove with bombs.
You will notice that the ground is split into two pieces when the battle begins, but it will come together when Rat is about to change his attack. He will fly in the foreground to the other side of the screen, then swoop down back across. This is your chance to either leave a bomb in his path, or trip him up with the Knight's shield, leaving him vulnerable for a bomb. You should likely see the icon for using the Cherry Tree Head during the battle, so use it to get the CEDAR COUPLE HEAD.
Doing so will make leaves appear, that you can use to reach a platform, where you can hit the rest of the sludge on the trees. Once all of them are gone, Rat will hover in the air and spew flames from his jetpack. Use the leaves to get above Rat and drop a bomb onto him, not once, but twice. This will make him emit smoke that you can use to reach him and finally finish him off. Note that when he's on the ground after this, hit him with Pikarina to get the RAT HEAD.
