Berate them for eating all your pizza.

"How dare you eat everything without saving any for the person kind enough to share with you!" Before you know it, you're shouting, and the words won't stop coming out. "You're inhuman! You're savages! You're monsters with no regard for decency or the sanctity of human life!" It's not until you see them both crying that you manage to pull it together. You've broken their little hearts! What will you do now?