Two food dishes:
One says "CAT" or "HERS" on it, with a very chewed tennis ball in it, and possibly a fork stuck in the tennis ball.
The other says "DOG" or "HIS" on it, a spilled open bag of catnip in it, and possibly a spoon sticking out of the bag of catnip.
******
OR:
A dog collar, and a cat collar, attached together by the same leash-- no handle end on the leash, just two ends that have collar attachments.
The collars could have heart shaped pet tags that say something appropriate on them... PUPPY and KITTY might be a bit banal.