I used to help my mom petsit (babysitting, but with animals) for a farm. It's called a Jolly Ball. [link] You can tie it to the end of a rope and hang it from something, or leave it loose on the ground, and it's supposed to be vastly entertaining. [link]
It's a uhm... hmm... looks like a uh... uuuuhhh... a wheel on top of a pole with two balls hanging from it? Some sort of torture device from Equestria's dark ages perhaps, touched up with a bit of paint?
[link] Wheel... of... TORTURE! Among tonight's contestant, only one of them will be let free. The others will be tied to a wheel and beaten with hammers.