Ok, imagine yourself as a 13 yr old, prone to mischief, and are out trick-or-treating.
You go door to door, ringing the bells and shouting "Trick or Treat!" and the nice home-owners give you gobs of candy. Yum, yum... a sugar high for the next month!
You come upon a house, ring the doorbell, and no one answers. The car is in the driveway, the inside lights are on, so you KNOW someone is home. You ring again. You ring again. You ring again.
Finally, some one comes storming to the door and grunts to you: "No candy here! Go away!!" Then, he slams the door at you.
Well... it IS trick-or-treat night. And technically, if someone doesn't give you a treat, you have the right to trick them... right?
What big-time prank are you gonna pull on them? How will you get your revenge???
[A quick word: This is just to be silly. I'm sure that we are all moral people out there who would NEVER dare to pull a big-time prank on someone who doesn't share an awe of Halloween. Nonetheless, be creative!]