ALTHOUGH the origins of the first day of April, April Fool’s Day, are obscure, it is still customary for practical and harmless jokes to be played on this day.Over the years, there have been some absolute classics — perhaps the best known being the great spaghetti harvest. On April 1, 1957, the British Broadcasting Company (BBC) reported on its news programme Panorama that Switzerland was experiencing a bumper spaghetti harvest that year, thanks to favorable weather and the elimination of the dread “spaghetti weevil”. Staged video footage which showed people plucking strands of pasta from tall trees was so convincing that many viewers called the network to ask how they could grow their own. The broadcast remains, by far, the most popular and widely acclaimed April Fool’s Day hoax yet.On the Internet, hoaxes are standard fare although a few notable pranks stand out and tend to be reposted year after year.A 1996 announcement was to the effect that every computer connected to the World Wide Web must be turned off and disconnected for “Internet Cleaning Day”, a 24-hour period during which useless “flotsam and jetsam” is flushed from the system.In 1962, Sweden’s Sveriges Television brought its technical expert, Kjell Stensson, onto the news to inform the public that, thanks to new technology, viewers could convert their existing sets to display colour. At the time, there was only one TV channel in Sweden, and it broadcast in black and white, so this was big news. Stensson explained that all viewers had to do was pull a nylon stocking over their TV screen, and the mesh would cause the light to bend in such a way that it would appear as if the image was in colour. He proceeded to demonstrate the process. Thousands of people were taken in.1976: During a morning interview on BBC Radio 2, the British astronomer Patrick Moore announced that at 9.47 am that day, a once-in-a-lifetime astronomical event was going to occur. Pluto would pass behind Jupiter, and this planetary alignment would temporarily counteract and lessen the Earth’s own gravity. Moore told listeners that if they jumped in the air at the exact moment the alignment occurred, they would experience a strange floating sensation. When 9.47 am arrived, the station began receiving hundreds of phone calls from listeners claiming to have felt the sensation. One woman reported that she and her friends had risen from their chairs and floated around the room.