Theo doesn't get kongs anymore (I'm too lazy, and he doesn't need the excitement). But he got so adept at emptying them that I ended up having to make a mixture I called Kongkrete--kibble, water, and peanut butter microwaved and beaten into a paste and then frozen. It was the only way to keep him occupied for more than five minutes.
I'm gonna try yogurt and banana and peanut butter. Maggie will enjoy that I think.
I stopped with the marshmallows. She started begging too much for them. It was like she was getting obsessed with them. (sugar!) Even though I only gave them to her a few times in the kong. She would not eat anything else in her kong. Crazy dog!
I usually only freeze if the filling is runny (yogurt, applesauce etc). Lasts longer!
Lately I've been stuffing Henery's kongs with chopped up apple and banana, mixed in with his kibble, parfait-style. This way he can enjoy them wherever in the house (ie. I don't have to crate him, like I have to with the frozen ones).