It’s not a real thing. It’s just a parody to lighten the mood. I think it’s just when someone is deep in thought, they aren’t always cognizant of their facial expressions and if they happen to be thinking of something annoying or irritating, they make other people think they are annoyed at them when they really aren’t, or at the very least, that they aren’t paying attention to what the other person is saying. (which might well be the case!) Like I said before, there’s lots of appropriate responses. “I’m fine.” “I was just thinking.” “Sorry. I was distracted by something.” However, if this is something that happens to you a lot (like more than once or twice a week) you might want to try to be more aware about it, particularly if you are at work and you know you are in a bad mood, because most people aren’t actually going to say anything to you about it, but that doesn’t mean they don’t notice it and it doesn’t effect how they perceive their interaction with you.