Gipper sometimes get a little agressive, but nothing more than a growl or a nip. It ususally comes when he gets woken up from a nap outside of his crate and someone other than myself tries to put him up. When he's already awake, he's fine. Also, I've noticed that he is virtually perfect when it's just me and him, or him and my roomie- basically when it's him and one other person, he's the most mellow, relaxed little gentelman you'd ever meet. But when two people are there… it takes about a half hour for him to calm down and quit jumping and wanting to rough-house. I try to wrestle with him for about five or ten minutes a day, to let him have some play time, all the while pinning him, letting him know that I am still the "Alpha Male" and always will be. It seems to work really well, because he's getting better and better as each day passes.