I'm noticing the second cat in the avatar.
He is showing a great deal of interest in the proceedings.
Not sure if it was to catch the strange moving "prey" or just watching to make sure it wasn't next.
And that first one sure looks a lot like a ferret as it goes by...
BTW. A completely harmless trick to pull on a cat. gently tie a dish-towel or light duty cloth around the mid section of a cat. It won't be able to walk or balance on it's feet. Looks a lot like it is drunk.
It seems that a cat has some hairs on the mid part of the body that help it keep it's balance. When you tie a cloth around it and press those hairs flat against it's body it can't stand.
Just be warned ! Take it off fairly quickly or the cat may figure out that you did it and take it's frustrations and anger out on you.
Not the kind of fun that is worth stitches !