My cats, especially the one in the ID pic, will play with anything that slides across the floor. I find their toys, empty thread spools that I give to them, leaves that manage to get in the house, in the oddest places. Cats just like movement and anything that rolls like a pen is a real hit with them. I cleaned out a hall closet last week and found a spool, a cat toy, and one other item that had managed to slide under the door that he was playing with.