My three cats love to play. They are pretty good about not breaking things, but they get upon shelf units, the computer monitor (for climbing on said shelf unit near it) and lots of other things.
A friend of mine sent me a gift package for the holidays. Included were a ceramic bowl and a wooden spoon, which my friend thought I could use on my altar. At first, I had them on my kitchen table, after I opened the box. Thunder, my youngest cat, who is now 11 months old, liked playing with the spoon. I moved the bowl and spoon to my altar, but I was wondering if he would just take it off the altar and continue playing with it. I began to notice that my cats never seemed to touch my altar at all. Nothing on the altar had ever been moved, including the bowl and spoon after I put them on it.
My incense burner had been knocked over, but I had placed it on a glass shelf for a while, and it got knocked off, but the altar and the items on it have been left intact.
I believe my cats know that the altar is a sacred place and that they respect its importance.