I know that the world is pretty broadly divided into cat people and dog people. And we already have three hounds as sidekicks in Doomtown. People know that a dog would take a Bullet for them. And the indifference of cats is well documented (meme'd) on the internet.
Scratch here, can go both ways. If her "owner" is in a shootout that she has no interest in, she can promote a nearby dude as her new caretaker. Or Scratch can see a fight breaking out and decide to wander into the middle of it.
The card cycle is to represent a luck aspect. Possibly even a deliberate sacrifice play to get better cards into hand (and recycle a 5 of hearts).