What is it about the plastic rings off of milk jugs that cats find so intriguing? Mine love them ( my male cat often becomes aggressive and begins growling when he gets ahold of one), and i hear that they are a fairly common favorite toy among other cats too. There are many other somewhat similar items i've given my cats that fail to elicit any real interest, but the actual milk jug rings get them every time. could there be some kind of milk scent on the rings that gets their attention? or is it something about the shape?