One of the most fun things about Halloween are the costumes. The tradition is rooted in the notion that on Halloween night, the veil between the worlds of the living and the dead is very thin, allowing all sorts of entities to cross over. People wore scary costumes so that the evil spirits would think they were one of them and not do them harm. In modern times, however, things have changed significantly. Nowadays we often dress up as things we admire and want to be. We enjoy putting on a face, and stepping into a role, just to see how it feels. We emulate, and we also make fun.
This is a cover of a Michael Jackson song, and the whole video is exactly that: emulation, and making fun. Everyone is dressing up in homage to Jackson, delivering tricks as well as treats. This is “Smooth Criminal” by Alien Ant Farm.