I bought the pink teething puppie kong, for Christabel. I fill it with her kibbles and put a little peanut butter on the opening, then freeze. When I have to leave her in her crate I give it to her. It's always empty when I come back. As far as playing with it, I have never seen her with it and she always leaves it in her crate unlike the other toys (she'll bring them out and play with them). I think she knows it's her busy toy for when she is in her crate.
http://media.zooplus.com/bilder/pupp...ng_puppy_1.jpg