In 1969 the Dutch Television broadcasters did an April fools joke, they said they could detect people that did not pay for watching TV (zwartkijkers) by driving

In 1969 the Dutch Television broadcasters did an April fools joke, they said they could detect people that did not pay for watching TV (zwartkijkers) by driving around with a detector [0]. It could be blocked by wrapping your TV in aluminum foil. The next day aluminum foil was sold out in many places... [0] https://historiek.net/1-april-grappendag/1070/ https://historiek.net/1-april-grappendag/1070/