When were gremlins invented?

During World War II. Airplanes (after a while of use) started to fall apart. Nobody knew why this was happening so they invented the gremlin. A imaginary creature that sabotaged airplanes. Now-a-days we know it to be due to metal fatigue.

You are right, gremlins were invented during World War 2. Their primary purpose was to tamper with the control surfaces of War planes while at 30,000 Ft over enemy territory. After World War 2 they were out of jobs so they moved into the Auto repair business & made life pure hell for Auto Mechanics! (I am an Auto Mechanic) (Cotton Picker)