J.H.
My 18 month old thinks it's hilarous to pretend he is a dog. He crawls around and even says "woof, woof!" He will play in the dog dishes, too (though he hasn't actually eaten dog food yet). He learned this behavior from his older sister, who also likes to pretend she is a dog. He is copying her more than he is copying the actual dog, but it's the same type of behavior. I think it just shows that they have imagination! I wouldn't worry about it.