- Alabama Changes the Value of Pi: The April 1998 newsletter of New Mexicans for Science and Reason contained an article written by physicist Mark Boslough claiming that the Alabama Legislature had voted to change the value of the mathematical constant pi. This claim originally appeared as a news story in the 1961 science fiction novel Stranger in a Strange Land by Robert A. Heinlein, however see also the actual Indiana Pi Bill.
- Spaghetti trees: The BBC television programme Panorama ran a famous hoax in 1957, showing Italians harvesting spaghetti from trees. They had claimed that the despised pest, the spaghetti weevil, had been eradicated. A large number of people contacted the BBC wanting to know how to cultivate their own spaghetti trees. It was, in fact, filmed in St Albans.
- Left Handed Whoppers: In 1998, Burger King ran an ad in USA Today, saying that people could get a Whopper for left-handed people whose condiments were designed to drip out of the right side. Not only did customers order the new burgers, but some specifically requested the “old”, right-handed burger.
- Taco Liberty Bell: In 1996, Taco Bell took out a full-page advertisement in The New York Times announcing that they had purchased the Liberty Bell to “reduce the country’s debt” and renamed it the “Taco Liberty Bell.” When asked about the sale, White House press secretary Mike McCurry replied tongue-in-cheek that the Lincoln Memorial had also been sold and would henceforth be known as the Lincoln Mercury Memorial.
- U2 Live on Rooftop in Cork: In 2009 hundreds of U2 fans were duped in an elaborate prank when they rushed to a shopping centre in Blackpool in Cork believing that the band were playing a surprise rooftop concert. The prank was organised by Cork radio station RedFM. The band were in fact just a tribute band called U2opia.
**Information on April Fool’s Day provided by Wikipedia**