You'll notice that Hera is wearing a collar while Lightning remains a Nature Boy. That's because Hera has figured out how to use the pet door and likes to spend a lot of the day outside. Lightning is a scaredy cat about outdoors and wants to stay inside (the better to get into things). So Hera has to wear a collar with her tag on it, to show people who might see her that she belongs to someone.
Hera and Lightning find their high rise a lot less roomy than it used to be.