These are the Pokeball bath bombs made and sold by Etsy shop FizzyFairyApothecary (which is currently on hiatus). They cost $5.50 apiece or you can get a whole set including a regular Pokeball, Ultra Ball, Net Ball, Great Ball (I have two!), Premiere Ball and Master Ball for $30. Each 2.75" ball fizzes and dissolves in water, releasing its particular scent, dying the bath water, and revealing a little Pokemon toy. What you do with that Pokemon toy afterwards is your business, but I suspect jamming it up your keister is a valid option, especially considering you're already in the bath and all warm and slippery. Are you fingers pruney? I bet your fingers are pruney.
Keep going for several more shots of the options.