What's behind your back, Jack?

Jack thinks he's being sneaky.  If he has something he's not suppose to have, he will put it behind his back as soon as you look at him.  It's usually something I've already told him no to (marker, thermometer, candy, whatever).

Me: "What's behind your back, Jack?"
Jack: He'll shrug his shoulders and make an "I don't know" sound.
This is when I usually give my well-practiced stern mother look.
Which is then followed by a big mischievous grin by Jack.  Then in his sweetest voice, he'll say, "Hi," as if that's going to make me forget he's doing something wrong.
I continue with an even more furrowed brow and mean look.
This then prompts him to chunk the object away quickly, hoping I didn't see him in the act.
He'll then walk over to me and give me a big kiss to butter me up so he won't get in trouble.

Little Stinker.