Walkthrough
By activating the Hidden Switch in Reef Resort, you will unlock the extra stage of Inside Islands. Simply based on its name alone, Inside Islands are a number of different miniature islands you must pass through, including a few more pools of Water. This stage is home to two more Mini Boss Battles, as well as the first level to feature the Como and Spider Copy Abilities (along with the Friend Bounce).
After passing through the second door of the level, you will come to an area where you must climb upward. Eventually, you will come to three Spikey Enemies that are each next to the other on the left side. Use Kirby's Spider Friend Ability, allowing you to boost one of his allies upward to open a pathway to the treasure cheat shown. This is where the level's Rainbow Puzzle Piece is found.
Directly before finishing Inside Islands, you will be faced with the task of battle the Mini Bosses of both Bugzzy and Mr. Frosty at the same time. Like the first encounters with these two, they are pretty easy to defeat. Just keep attacking them, as that usually does the trick, and quite quickly no less.
Copy Abilities
Bomb, Crash, Ice, Plasma, Sleep, Spider, Suplex, Water, Whip
Blipper, Bomber, Cappy, Como, Coner, Driblee, Glunk, Gordo, Grizzo, Mamanti, Noddy, Nruff, Plugg, Poppy Bros. Jr., Scarfy, Squishy, Waddle Dee, Wester
Bugzzy, Mr. Frosty