What 'cha doin'?

I work at a church which also houses a day school, and every once in a while I get trapped with a small child, usually when I in the restroom washing my hands or trying to pretend I'm not in one of the booths.  Invariably I get the question -"What 'cha doin'?"  Rather than give in to the temptation of grumping "What do you think I'm doing?" I've taken to giving answers like "I'm paddling my row boat to China." or "I'm in a rocket heading for the moon." or "I'm hopping up and down on one foot."  The reaction is always a long pause followed by "Nuh uh." usually with giggles.  Always leave 'em laughing.