I had created an interesting geometric coin trap that requires no supports to print and uploaded it about a month ago, but then when I saw the “cat toys” design contest - the concept of a coin trap that could also freely roll around (enticing the cat to chase the shine and rattle of a couple of caged coins) seemed like a fun idea to submit.  

Unlike that other coin trap though, this one definitely does require supports to print (for the prints shown in the pictures I used the “Snug” supports style in the Prusa Slicer, with the “Support on build plate only” option).  To make it more durable, I'd also recommend setting the “Vertical Shells → Perimeters” setting to 5, and “Infill” to at least 30%.  Any layer height and nozzle size should work fine.  I've also attached the 3MF file that shows the settings I used if you'd like to start with that, as well as the “gcode” I used to print this on my Prusa Mini.

The inner sphere of the toy will permit a coin up to 36 mm in diameter, while the sides will only allow a coin under 22 mm to escape - making it a perfect little cage for a couple of US Quarters or Euro Coins.  You'll want to drop the coins in about half way through the print by simply pausing the print, or just throw them in while the printer is in action for an extra challenge.  The quicker you can drop them in the better, as you don't want to let the plastic cool down too much in order to ensure good layer adhesion.

This simple toy beautifully shines, rattles, and rolls.  I hope you - but more importantly your cat - enjoys!