Sponge Cave Spelunking

Sponge Cave Spelunking is the third level of the game Yoshi's Woolly World. It introduces Chomp Rocks.

Enemies

 * Piranha Plants
 * Nipper Plants
 * Nipper Spores
 * Shy Guys

Smiley Flowers

 * 1) Smiley Flower #1: In the first cave section, free the Jump Block from the dirt to use it to jump up to a room with it.
 * 2) Smiley Flower #2: In a crevice above the blue dirt in the down-hill section. Aim a yarn ball directly to the right to access it without destroying too much of the dirt from beneath it, so leaving a platform you can reach it from.
 * 3) Smiley Flower #3: After rolling the yellow Chomp Rock down a series of hills, you will find yourself in a small tunnel, pushing the Chomp Rock into Piranha Plants. Before pushing the Chomp Rock out of the tunnel and into a more open area, jump on top if it and use it to reach an area hidden in the roof of the tunnel.
 * 4) Smiley Flower #4: Immediately after collecting the third Smiley Flower, drop down from the hidden area and push the yellow Chomp Rock as far right as you can into a small hole in the floor. This will activate a hidden cloud. Throw a yarn ball at the cloud to reveal new toadstool platforms leading to the ceiling. Break the blue dirt on the ceiling to let a yarn present fall through the gates. Unravel the yarn present to reveal Smiley Flower #4.
 * 5) Smiley Flower #5: When you reach a vertical section with blue dirt and Nipper Plants, the final Smiley Flower is in the top-left corner, in a hidden area behind the wool wall. Shoot yarn balls or jump to break the dirt to reach the upper left corner. The hidden wall is the very topmost left panel, so try to leave some dirt beneath it to stand on, to be able to reach this. If you've shot away too much, clear away all the dirt, and flutter jump from the platform with the upward facing arrow.

Wonder Wool
Collecting all five Wonder Wools in the level unlocks Circus Yoshi.
 * 1) Wonder Wool #1: Right at the beginning, take the Chomp Rock left and destroy three blocks guarding a room. It is in there (Purple)
 * 2) Wonder Wool #2: After the first pipe, in the Piranha Plant section, use a Yarn Ball to make a stairway going up where there is a Winged Cloud. It is in there (Light-Blue)
 * 3) Wonder Wool #3: In the section where Nipper Spores first appear, jump on the last red platform to make a Winged Cloud appear. It makes platforms which leads Yoshi to a space with a pipe he must activate with yarn balls. Go in, and it is in the room it leads Yoshi to. (Pink)
 * 4) Wonder Wool #4: After the downhill section (where you collected Smiley Flower #2, look for a patch of blue dirt at the bottom of the screen underneath two toadstool platforms. The dirst has a few yellow crystals beneath it, showing that a ground pound through the dirt will not lead you to your doom. You'll find a large cave with a winged clud that reveals the fourth Wonder Wool. Use the Jump Block to exit this cave and continue the level.(Red)
 * 5) Wonder Wool #5: When you reach a vertical section with blue dirt and Nipper Plants, the final Wonder Wool will be visible, but accessing is not immediately obvious. Ascend a small way, until you can see a section of dirt underneath a purple toadstool platform. Shoot yarn through the dirt to access this area beneath the peuple toadstool platform. Groundpound through the dirt beneath you, trot left a bit, and you have the fifth Wonder Wool.(Purple)

Trivia

 * Part of this level's background music can be heard in the remix titled "Yoshi's Woolly World" in Super Smash Bros. for Wii U, which pre-dates Yoshi's Woolly World.