These shy spirits inhabit Mario’s world and have been known to vanish or freeze when met face-to-face. In recent years, they seem to have overcome their fears in order to pursue tennis and other social activities. They usually appear in groups and fly in formation. From time to time, giant Boos make surprise appearances!
Compatible games and functions: https://www.nintendo.com/en-gb/Hardware/amiibo-/amiibo-details/Boo-1125632.html