Gremlin birth. 1) Mogwai-> mogwai. You'e a heartless wretch if you didn't want to vomit while Gizmo was screaming. 2) Pupa-> gremlin. Giant slimy bug-looking things cracking open while Gizmo hides in the motorcycle helmet. 3) Gremlin-> gremlin. Watch the scene with the lightning gremlin and the fire hose. Then try to take a shower without scrubbing your back furiously.
"And that's how I found out there's no Santa."
Take the already dangerous and ubiquitous power of electricity and give it (semi-)intelligence and self-control. Oh yeah, and make it evil. Probably one of the most terrifying gremlins when you think about it.