Escalator Gremlins: These tiny creatures are a sub-species of the common gremlin (subhominus dahlen) which believes itself to be benevolent. Unlike its malicious cousin, it tries to help humans by sabotaging dangerous machinery. Unfortunately, its small cranial capacity (the average escalator gremlin is only three inches long from head to toe) has led it to the erroneous conclusion that escalators are dangerous. They do look dangerous, after all--they're all ominous and black, and they move in a vaguely disturbing way (as any small child who's worried about being sucked into one can attest.) As a result, the escalator gremlins make it their mission to disable escalators in high-traffic areas.
Contrary to popular belief, escalator gremlins have no grievance against elevators--in fact, they find the little chime that sounds when the doors open to be quite soothing. They do everything within their power to ensure that said chime occurs at every single floor, whether the elevator is going up or down.