In the interest of passing time (as opposed to passing gas), I got the ol' laser pointer out and started
Being the older of the two, Elf has mostly caught on that the damn laser dot can't be caught -- though she can't resist trying every so often.
Radar, on the other hand, still thinks that she can catch it with enough stalking, sneaking up on it, and pure enthusiasm.
Consequently, there comes a point where Elf gives up on the chase, and just lays down while Radar is still in full catch-it-kill-it mode.
Being Evil, I today I ran Radar around for a little while by frequently enticing her into thinking she almost managed to catch the dot. When she finally began to get tired and lose interest, I simply HAD to try one last thing: easing the dot over to where Elf was stretched out and wiggling it around ON ELF.
Normally, Radar would have enough sense not to annoy Elf to excess; after all, Elf is roughly 3X her size. But after coming so close to actually catching the dot, having it wiggling around and tormenting her proved to be too much: she just had to try to pounce on it. Being the unwilling and unwitting pouncee didn't sit well with Elf, and she commenced to giving Radar a sound thrashing. Apparently feeling she was being unjustly penalized for her actions, Radar began to fight back. While neither of them used claws or bit, there was still enough wrestling, slapping, jumping-on, and other combat to last a good five minutes, followed by another ten worth of getting in the "last word" via exchanging ambushes.