All of mine do this. Dogs and cats and other animal. I wouldn't worry about it. Personally I find it irritating, so I don't interact with it when they do - I just ignore the behaviour (not the kid) and do not pander to their 'requests' to be treated like the animal. But that really is just because they can get very annoying, if you give in once and play along they expect you to keep on playing - easier just not to get involved. So they play with each other instead. (but I'm just a grumpy pregnant 'unfair' un cool mum ).