This prop really does contain high voltage and is extremely dangerous; using any of these designs is entirely at your own risk. High voltage should always be treated with respect, and should only be used with the proper safety precautions.
This prop has an extremely loud sparking sound, along with movement and light to startle guests. It's remotely triggered via a small RF fob. It also features a small speaker with a constant 60hz buzz, to make the guests uneasy as they walk by it.
The prop is powered by a custom PCB with an ATmega328p chip (an Arduino, basically.) The sparking is provided by a high voltage coil from AliExpress.
Along with the flashing from the spark, there's also fiber optics run up into the wire that moves. This provides the illusion of the spark being much closer to the guest than it really is.
Video on YouTube.
Arduino source code available on Github.
Schematic and PCB layout available on EasyEDA.