Yep. Tried that. The cats will stick their head in, grab the treat and split.
Not sure. But someday they might changeWhat else could I put in that they'd like? I put it in front of the electric fireplace where they like to sleep, I put in a towel they've slept on, I put in toys they play with. I even sat with it in my lap. They won't have anything to do with it (it's a plush circular-form bed). So I sometimes use it as a foot warmer (and it really is comfy used for that).