Walkthrough
After completing Green Gardens, you will then proceed to Donut Dome with Kirby. Donut Dome is basically an underground cavern, being a darkened subterranean area that is lit by a number of torches. This is the very first level that you will be able to perform the Ice/Splash Curling Team Up Attack, done by combining the Stone Ability with either the Ice or Water Ability. If you're looking to get through Donut Dome with ease, then definitely stick with using the Stone Copy Ability.
After heading down the long hill once you receive the Stone Copy Ability, yet just before the third door, go to the left and use your Stone Copy Ability to hit the stump sticking out of the ground. This will reveal a hidden door. Once instead, make sure one of the other characters has the Ice Ability, allowing you to then hit the stump out of the right wall. From there, grab everything that falls down from it, including four brand new puzzle pieces.
Once you have done this, return to the normal path of Donut Dome. Just before the fourth door, head under the platform and strike the stump of the left wall (like before) to find the Rainbow Puzzle Piece for this level. After heading through the fourth door, proceed as normal. Just before you arrive at the fifth door, there will Hidden Switch (though not hidden at all in this level). Jump on the switch to activate. This is the first level to have a Hidden Switch; these switches reveal an additional level in the overworld. (This Hidden Switch will grant you access to Dream Palace, where the Dream Rod lies. The Dream Rod will allow you to summon an extra character to travel alongside Kirby on this journey.)
After activating the Hidden Switch, head through the fifth door in Donut Dome and proceed to the next level.
Copy Abilities
Bomb, Cutter, Festival, Fire, Ice, Stone, Sword, Water
Blade Knight, Cappy, Chilly, Driblee, Festival Bird, Kabu, Poppy Bros. Jr., Rocky, Shield Carrier, Sir Kibble, Waddle Dee