I think it's fair to say that cats and dogs aren't exactly the best of friends. In fact, I'd go so far as to call them straight-up rivals.
I speak from experience here. My own four-legged fur babies have never seen eye to eye, especially when my dog makes the mistake of trying to play with my cat who has no interest partaking in such utter foolishness.
But just because we've known most cats and dogs to be mortal enemies doesn't mean there aren't any exceptions out there.