A frustrating activity

So the latest activity for my Roo seems to be the newfound 'gift' of sneaking things he feels he is entitled to.
Case in point: Tuesday afternoon Roo was picked up from the bus by his grandfather, a favorite thing!! Grandpa brought him home and gave him yogurt and a banana for a snack. Being the only child in the house, there was no argument about what was for snack. A while later, sister and brother arrived at the house with Grandma. There was no offer of yogurt or a banana for the elder children, and Grandma gave them permission to have a cookie while she was preparing dinner.
After realizing that the elder children received COOKIES from Grandma, Roo decided he was entitled to cookies as well, although he had already eaten yogurt AND a banana, and it was nearly time for dinner. Grandma refused, telling him that after dinner he could have a cookie.

So... whilst everyone else was busy in the house, Roo took the box of cookies and ate them ALL (TEN COOKIES!!!) and helped himself to not just one, but TWO cans of soda as well.
Of course, at dinner time, he was not hungry and did not finish his meal. But Grandma, being Grandma, felt that perhaps she had given him too much food, and allowed him to not finish his plate.
After dinner, Grandpa gave him ice cream!! And you can bet that he ate EVERY SINGLE BITE!!

Is it any wonder the child was wired for sound?
We're all a bit wiser now that the empty cookie box and empty soda cans have been found stuffed behind the piano and couch - the snacks and drinks at my house are now under lock and key, and Grandma and Grandpa are doing the same.

Little stinker....