We tend to use strange metaphorical expressions for descriptions of one another. For example, “you’re a fat cat” means you should probably cut back on your daily McDonald’s burger with a large fry. The cat part refers to how sometimes cats will become obese by overeating. Welcome to America where the animals are just as unhealthy as us!
This is only a saying; many phrases as these exist, and they originate from everywhere in the world. One such as “grinning like the Cheshire cat” implies you’re smiling like a goof, or that your smile means you’re up to something. If you’re gonna smile, at least try to contain your pearly whites somewhat.
“The cat is mighty dignified until the dog comes in.” It basically means means humans are going to play nice and sweet until our worst enemy comes into sight. This is true, no? Not that it occurs often where I live, but how many a time have you gawked at someone’s sudden change in emotion and posture when someone he or she hates is nearby? Surely you’ve noticed how insults suddenly cross their mouths and how electricity seems to zip through the air. Quite the same with cats and dogs, really.
We all have that one so called friend that you have for no reason. Your group will talk bad about that person or fights may even happen on a regular basis; however, what about the time when he or she isn’t around? “When the cat is away the mice will play.” You always seem to have a better time without that certain one as well as everyone else. In this case we seem to be more like the mice (unless you’re the unfortunate friend).
We as humans have more in common with cats than you think. We are sly, clever, mean, and occasionally goofy.