When he was in the Peruvian Amazon recently, entomologist Aaron Pomerantz came across the "craziest caterpillar [he'd] ever seen."
Whenever the caterpillar was disturbed by a loud sound, its four tentacle-like arms would pop out. You can see it for yourself in this video.
Pomerantz explains in a blog post how he came across the unusual creature.
I might never have noticed this small brown insect had it not been for its unusual movement: noises would cause it to fire its tentacles in randomized directions, then slowly twirl back into a spring-like "ready" position to await its next alarm. This reaction to noise was so peculiar that once my group joined me around the creature, we proceeded to take turns yelling at it and filming its contorting reactions for over an hour.