The youngest of all the creatures in the monster pantheon, gremlins were born in the United States. Highly mechanical, they have been responsible for much technological progress. They live around tools and inside machines and appliances. The name gremlin comes from the Old English word 'gremian' (to vex).

The original description of gremlins were that of tiny humans with elf-like ears and yellow eyes, wearing miniature overalls, and carrying tools sized for them yet somehow still eligible to be used as if they were the correct size. Nowadays there is a more popular image of gremlins. Short beast-like creatures with very large ears, like that in the movie Gremlins.

During World War II, however, gremlins turned against mankind when mechanics and scientists began to take credit for gremlin work. They began by causing mechanical failures in aircraft at times when it was most needed. They did it to both sides of the war, proving indifferent and taking no sides in the conflict except that against humans.

Gremlins torment humans by blunting tools, pushing hammers onto thumbs, playing with the hot and cold water in showers, holding down the toasting mechanism and burning toast, and deflating tires. A skilled gremlin can cause a human mechanic to take apart a whole engine before he realises the fault could have been corrected by the tightening of one screw.