On the whole, I think the little standoffs were momentary, but once in a while, Gandalf would become too aggressive with the cleaning activities and Taffy would get miffed. If it looked like a fisti-cuff was about to start I would say sternly "Cats! Cut it out" at which they would both turn and look at me with a "Whaaaat?" look. It did stop any serious altercations, however.