I know this post is a few days old but I just wanted to add that we had 3 adult cats and received a very old but still playful ferret who all played happily together. Well sort of, the ferret tried hard to get the cats to play but usually the cats just looked at him like "What are you and what do you want??" But I occationally caught them playing together. Only had the ferret for a little while though because he had, what's it called that ferrets cat a lot? He went stiff and had seizures and screamed on and off and then died a few days later.