AmberLee, I don't know if it is new to them, it is the first time I have oberved this type of playing. Since it is raining outside, and the noise the rain makes on the metal awining, causes my furkids to be a bit "frisky", (more like aggressive). I've noticed this type of frisky behavior before, whenever it is raining. They have chased each other through the house before, but this is usually done while I'm busy with other things, and am too busy to watch them. But what caught my attention is the structure of theiir game, which appeared to me to be fairly complicated.