What Is stupidest reason why a friend has been mad at you.?

My friend is a cat freak. I mean she is just obsessed with cats. There was this joke one of our other friends made and it had to do with the look in cat's eyes and how sometimes they like give you the evil eye. She made this really funny impression of it and I laughed because it was hilarious. But my cat lover friend was there and she didn't get mad at our other friend at all but instead she got mad at me for laughing. I mean, it was just a joke and of course cats don't really look like the impression my friend gave but she refused to talk to me for like the next 3 days.