Once when I was a kid I brought a kitten from a family give them away... I put it on the counter and my female adult cat tried to attack it. My mom's dog and her puppies just stared at it and barked happily at it. My mother made me take it back since it wasn't quite weaned yet... Well that and she was a afraid that that the cat we already had would kill it or the puppies would injure the small kitten playing with him.