Fun:Tommyknocker
Tommyknockers are little dwarf- or gnome-like creatures who live in underground mines. They are tricksters prone to playing practical jokes on miners but are actually very friendly little critters. Miners know to leave a little of their food out for the tommyknockers. In turn, the tommyknockers watch out for the miners and are known to knock and otherwise make loud noises to warn miners just before the mine is about to collapse or explode. Many miners owe their lives to heeding this warning from the tommyknockers.
Born again Christians think tommyknockers are demons. They sometimes call in the preacher from the First Church of God With Signs Following (a/k/a GHOSTBUSTERS!) for an exorcism if they think they are tommyknockers in the mine. This action is met with near universal contempt from the nonbelieving heathen miners, who rather like having the little fellas around.
In Germany they are know as kobolds - the origin of the name of the metal "cobalt".
Please be friendly to the little fellas and accept their tricksy practical jokes in the spirit they were offered. They aren't bad creatures. Now born again Christians, on the other hand...