Reverse trick-or-treating
by Cory Doctorow from on (#S96P)
https://www.youtube.com/watch?v=xhS_CjECO90
It's when you carry a frame and door to someone else's door, while dressed as someone who's staying at home and giving out candy; you interpose your door between you and their door, ring the bell, and when they answer, they're confronted with your door, with a PLEASE KNOCK sign. They knock, you open up, and offer them candy. Trick-airity ensues. (via Reddit)