No one ever believes me when I say this, BUT: this is not kitty arousal! Cats, like most mammals, are ticklish! You and I would probably giggle and react with our sides tickled, but that spot above their tail happens to be ticklish for them. Compare actual mating behavior to this and I'm confident you will find it is nothing alike. The cat makes "battle ears" because, well, I mean, you may like to be tickled but it also can be stressful.