Both the Bounce Ball and Cutting Board items have different effects based on which character is using it. Specifically, they appear to be affected by bust size. For example, characters with larger chests (i.e. Tsukomo Sana, Ouro Kronii, Pavolia Reine) will spawn larger Bounce Balls. Conversely, characters labeled as being "flat chested" (i.e. Gawr Gura, Natsuro Matsuri, Kobo Kanaeru) will spawn larger projectiles when equipped with Cutting Board. Both these items, and their effects, reference former hololive member Uruha Rushia, who would get upset at people for teasing her flatness, insisting that she is actually "boing boing" (the Bounce Ball references this onomatopoeia).