Maci loves her little Kong! We put the little peanut butter snacks in the Kong that the Kong makers have for it. It keeps her busy for quite a while trying to get out of all of the treat!
I haven't tried freezing anything in the Kong like peanut butter or yogurt, but that would certainly work. If I did that, I think I would have to give her the Kong outside. It might create a little bit of a mess when everything starts melting.
However, the little snacks work great! I would highly recommend getting one, but every dog is different on what they like. Not all dogs will go crazy over this toy!