soo..yea. young cat (4 months) and young dog (5 months). and of course they romp around ya de da. but sometimes phoenix (dog) yelps, im guessing maybe because river (cat) bit or scratched too hard? and then phoenix plays and will mouth (not really like BITE, but you know..just using their mouth) River, and i've caught him a few times kinda dragging him ( and i dont mean like DRAMATICALLY DRAGGING him across the room, but just moving) but rivers on his back, phoenix is over him, and he'll kinda shake (again, not like hard core shaking) or move river, and river like clamps on from behind and digs his claws underneath on phoenixs belly adn there will be scratches sometimes. and of course i dont want to wait for a dead cat or a dog with a scratched eye ball to figure out, hey thats enough! i yell for them to stop, and they'll stop. but sooner or later, they are at it again. and while it doesnt seem 'aggressive' at all. no growling or snarling or weird cat growls. its just..annoying sometimes, lol. i hope when they reach older age they just lay together and are nice. and phoenix doesnt yelp every single time they play. but sometimes. and of course phoenix doesnt seem to be drastically biting at river, i just dont want him to get out of hand and freaking puncture his neck and i dont want EITHER of them to hurt eachother. maybe just a kid playing thing? i dont know.