I have two cats that act in conjunction with each other as my familiars. While I am casting, they do some weird things- such as play with my altar cloth, jump up on the altar while I'm working on craft, etc. I had always wondered why cats do this and had decided to a little research.
My findings were: Cats think that if you stare at something for too long, they think you're stuck and they try to "free" you. This makes sense as to why cats stand for awareness. They keep you grounded and in the earthly plane. It's always good to have a cat around for this reason. While they do the stupid, sometimes enraging things, they only mean the best for you. Mine are always present when I'm doing research on magic for my craft or when I'm performing it and always try to break my focus a few times.
There are many other reasons why cats are good for us. According to some, cats are an omen of weather. If they stare out the window all day, it could mean that rain is coming. If they have their back to the fire (or in my case, the heater) it could mean a cold snap is coming. Black cats are often a symbol of death, based off a Roman soldier who killed a black cat in Egypt and was then killed by a mob of angry locals.
So, be sure your familiars are very loved. Whether they be a cat or any other creature, they're important to your craft.