The following can be used for Kirby Star Allies for the Swtich:
The Ultimate Choice mode (Soul Melter difficulty)
Complete The Ultimate Choice mode on Level 7 with any lead character and you'll unlock the Soul Melter difficulty in the Ultimate Choice mode.
Beat the game to unlock Theater mode.
When you beat the game, you'll unlock the Ability Planetm where you can grab any copy ability and Extra Planet Delta in the Far-Flung Starlight Heroes section in Story mode. Near the end of the Extra Planet Delta level, you'll arrive at a large background block with a cross and two dot platforms, and eagle eyed gamers will realize this is a game boy. Above, there's an empty space where a door will appear. Go through the door and you'll find a hidden Game Boy style level. At the end of that level , you will reach a large button. Stomp on the button to summon a giant statue of Kirby, with the words "We Heart Kirby" over his head. If you are using the Switch Joy-Cons, the HD Rumble will play Kirby's theme from the original Kirby's Dream Land on the Game Boy.
Secret characters in The Ultimate Choice mode
Beat the Ultimate Choice mode on any difficulty to unlock King Dedede, Meta Knight, and Bandana Waddle Dee as selectable allies in The Ultimate Choice mode.