Normally UFO is only available by using the Kirby series Kirby amiibo. However, after obtaining a 100% file, a UFO enemy will appear in the copy ability testing room for you to use in Story Mode. It will still be unavailable in the Arenas, however. Obtaining a 100% file entails getting all Code Cubes and beating Story Mode, clearing all stages of Kirby 3D Rumble and Team Kirby Clash, getting all stickers, clearing Meta Knightmare Returns, and clearing both Arenas.