Aww, sweet pussy-cats. You can never send enough pussy-cat pictures my way.
My cats are a brother and sister who've been together all their lives, so they usually get on very well, but even they can't resist a bit of rough and tumble now and then (even then it seems mostly very friendly compared to the displays of aggression I've seen them put on with other cats over territorial matters). What's strange is that it's usually the female cat, Cleo, who initiates the occasional brawl...strange not only because Scamp's a fair bit bigger than her, but because she has a meeker and much more nervous disposition in general than him - her brother's one of the few things that doesn't seem to intimidate her.