Bellybutton Appreciation Day

I must have missed it on the calendar this morning, but today seems to be international Examine Your Belly Button Day. In almost every class I have been in so far there has been at least one child (if not more) with his shirt pulled up to his chin and he's staring at his belly button. I know they are fascinating objects, and that we are learning to be scientists in kindergarten, but I'm amazed at the consistency of this action across the classes.