Sometimes I wonder if cats and dogs feel much pain. When our dog was a pup, she would crash into the patio door or something else many times a day, head first and never acted like it hurt. Now that our 2 kittens are well acquainted and playing together more, they crash into things or roll off the couch during a wrestling match, onto a wood floor and just keep going. I cringe whenever they do it. It gets pretty wild around here at times. Enya and Blaze love the stairs for chasing and wrestling. They're fun, but Blaze has to learn the house rules. He's doing pretty well. He isn't as persistant as Enya, which helps. I'm glad the intros went so easily and that they all get along well. I think our dog would love a house full of cats.