Something you say to lighten the mood. It has no literal meaning, just that you can say it in reference to a question or just out of the blue for a laugh. The way you mean it comes from your tone of voice!
also shibbity blibbitz. interj. Used in exclamation as a euphemism for shit, usually when one is about to say shit but realizes that someone is standing there that would not approve. From shit + jiminy cricket + blibbit (see links for more info).