This is a two-part kitty weeble wobble toy. In my pictures, I cast the bottom in concrete but here I've uploaded a hollow version so you can fill it with something heavy. I mixed iron powder into the concrete but I'm sure nuts or steel shot or coins would work as well!

I added the structure on the bottom of the top piece so it would adhere better to the bed, but you can always cut it off.

Weebles wobble but they don't fall down!