In the scene, Gazzy notices a metal plaque warning to stay off the third rail, and he is curious about its meaning. Fang explains that the third rail carries a dangerous high-voltage electrical current of seven hundred volts, which can be deadly if touched.
Fang emphasizes the danger by comparing the potential consequences to "human popcorn," highlighting how severe the shock would be. This exchange underscores the importance of paying attention to safety warnings around high-voltage areas.