This ball is intended to give your cat exercise as they eat their food.
I saw a ball like this at the pet store and, as I have extremely strong makerbot goggles, decided to design and print one.
It's taken her a while, but my cat is starting to learn to use it.
You will need your support settings dialed in properly for these prints. It will take some excavating after as well, but they turn out nicely.
Fill one half with dry food, and push the other half on. The two halves press fit together with some minor sanding, though you may not even need that.