Backwards Birthday Party
Face it, kids love Anarchy. Throw out all the rules, or better yet, invert them. You'll need a little time to indoctrinate the guests. "Hi" is "Bye" and "yes" is "no" and it gets confusing fast. Use the format for a traditional party, with games, food, etc and apply your new rules. Have the drinks out of a bowl (outside), and eat your pizza out of a glass. Serve the dessert before the main course, and hang the party decorations upside down.