What is the grossest thing your kid has done without knowing how gross it was?

A fellow jelly’s recent Facebook status prompted this question Shout out @ubersiren! What is the grossest thing your child, or a child you know, has done without realizing how truly gross it was? As an example, I was with a friend and her kids at a McDonald’s play area once. One of her kids came down with a band-aid on his arm that wasn’t there before, when she asked where he got it he pointed to the giant climbing apparatus! He picked up a band-aid another kid had left in there and put it on himself. Ewwww!!! Care to share your gross-out story?