1Bielefeld city conspiracy
April 1, 1999: As a result of a 20-year-old internet joke that the German city of Bielefeld doesn't actually exist, five years after the myth started to spread, the city council released a press statement titled Bielefeld Gibt es doch! (Bielefeld does exist!). However, the statement’s publication date of April 1, 1999 (April Fools' Day) was ill-chosen as it unwittingly played right into the humorous conspiracy. In allusion to the conspiracy, the 800th anniversary of Bielefeld was held under the motto Das gibt's doch gar nicht (colloquially “This can't be true”, but literally “This does not actually exist”).
2. April 1, 2004: On this day, Google launched invitation-only beta version of Gmail. At a time when most webmail services offered inbox sizes measured in single-digit megabytes, Google, already known for having April Fools’ press releases announced a service offering an unbelievable 1 GB of storage. They intentionally released a pun-filled press release announcing Gmail. In reality, it was a double fake, in that it was actually serious.
3. April 1, 1949: Newfoundland became a province of Canada just minutes after midnight on April Fools’ day in 1949. The induction ceremonies were originally set for April Fools’ Day in 1949, it having occurred to no one at the federal level that this might not be the most appropriate of dates. The date was then, at the eleventh hour changed, but it was too late to make the change, but Canadian Prime Minister did amend the Terms of Union by which Newfoundland joined Canada to read that this happened on March 31st.
4. April 1, 1985: Like the histories of all great rock bands, Van Halen’s past includes some landmark dates. On April 1, 1985, singer David Lee Roth shocked the rock world by announcing that he was leaving Van Halen to pursue a solo career. Though long-time fans likely hoped it was an April Fools’ joke gone terribly wrong, he did in fact quit.
5. April 2010: Director Joss Whedon was announced as the director of The Avengers. Fans that were both into Buffy and Avengers were angry because they thought it was perfect but it was probably an April Fools’ joke, and comics exclusive fans got real mad because they didn't want the creator of 'Buffy the Vampire Slayer' to plague the movie.
6Same-sex couples marriage
April 1, 2001: On April Fools’ Day in 2001, Netherlands legalized civil marriages for same-sex couples. It didn't have anything to do with April Fools’ Day.
7. April 1, 2015: Less than 24 hours before April Fools' Day, Amazon unveiled its newest innovation: the Amazon Dash Button. The gadget bears the logo of your favorite brands and sticks directly onto a flat surface in your home. When you run out of the corresponding product, you just push the button and a refill is dispatched to your house. The online community was sure it was a prank, but Amazon assured it was not fooling around.
8. April 1, 1997: Comet Hale–Bopp was perhaps the most widely observed comet of the 20th century and one of the brightest seen for many decades. It was discovered on July 23, 1995, and was expected to pass earth on April 1, 1997. It will next return to the inner Solar System around the year 4385.
9. April 1, 1944: Schaffhausen is located in a finger of Swiss territory surrounded on three sides by Germany. On 1 April 1944 Schaffhausen suffered a bombing raid by United States Army Air Forces aircraft which strayed from German airspace into neutral Switzerland due to navigation errors. About a hundred civilians were killed. The United States quickly offered four million dollars in reparations.
10. April 1, 2005: Comedian Mitch Hedberg was found dead in a hotel room in Livingston, New Jersey on March 30, 2005. Medical examiner’s office reported “multiple drug toxicity” in the form of cocaine and heroin as the official cause of death. Hedberg's death was formally announced on April 1, 2005, leading many to believe it was an April Fools’ joke, only to find out later that it was not.
11Sonic and Mario
April 1, 2007: Back in the day when Sega and Nintendo were bitter rivals, no one would have thought that their hit characters Sonic the Hedgehog and Mario would team up in a game. But that's exactly what happened when “Sonic and Mario at the Olympics” was announced in 2007. Sega and Nintendo announced it via a joint press release a couple of days prior to April 1, but fans just assumed there was no way it could be true. Soon after, Sega stated on their official website that the game is official and that both Sega and Nintendo are working on this game project.
12. April 1, 1947: When the media reported the death of King George II of Greece on this April Fools’ Day, the public largely thought it was fake, but he had really died of arteriosclerosis. He was succeeded by his younger brother, Paul I.
13. April 1, 1970: Apparently the announcement of the AMC Gremlin was too laughable for people to consider real. After all, who would name a car that? And a car expected to compete with the VW bug was just silly. AMC was serious, though, and the Gremlin was produced from 1970-1978.
14. April 1, 2003: The two biggest Japanese RPG franchises in video game history have been for some time Final Fantasy and Dragon Quest, created by the companies Square and Enix, respectively. On April 1, 2003, the two companies officially merged, creating Square Enix, a single company which would control all IPs of both companies, an undisputed JRPG supergiant. Though it was discussed and announced beforehand, due to the actual merge happening on the April Fools’ Day, many fans thought it was a huge joke.
15. April 1, 1983: Hooters, Inc. was incorporated in Clearwater, Florida, on April 1, 1983, by six Clearwater businessmen: Lynn D. Stewart, Gil DiGiannantonio, Ed Droste, Billy Ranieri, Ken Wimmer and Dennis Johnson. The date was an April Fools' Day joke because the original six owners believed that their prospect was going to fail.
April 1, 2016: In Lubbock, Texas a woman put her fingers under her sweater in the shape of a gun and said she wanted “all the money.” When the teller just stared at her the woman said, “April Fool’s,” and left. There were no injuries and no money was taken.
17. There was a man named Porky Bickar so dedicated to April Fools Pranks that in 1974, he flew hundreds of tires into Edgecumbe dormant volcano in Alaska and set them on fire, thereby fooling the local populace, and coast guard into thinking the volcano became active.
18. In 1957, the BBC aired an April Fools segment showing a family harvesting spaghetti from the family spaghetti tree. When viewers asked how they could grow their own, they were told to place a sprig of spaghetti in a tin of tomato sauce and hope for the best.
19. On April Fool’s day in 1976, BBC convinced many listeners that a special alignment of the planets would temporarily decrease gravity on Earth. Phone lines were flooded with callers who claimed they felt the effects.
20. When an online college in the US jokingly offered, as an April Fools gag, a course called 'Underwater Basket Weaving' (a notorious code for a do-nothing class) the school was forced to apologize for being disrespectful to indigenous cultures.
21Alex Trebek and Pat Sajak
Alex Trebek and Pat Sajak, host of Wheel of Fortune, traded places on April Fools' Day 1997. Sajak hosted Jeopardy! and Trebek hosted Wheel of Fortune with Sajak's wife, Lesly, as Trebek's co-host.
22. NPR posted a link “Why doesn't America read anymore?” to their facebook page; the link led to an April Fool’s message saying that many people comment on a story without ever reading the article and asking not to comment if you read the link. People commented immediately on how they do read.
23. Tom Moore Jr., a member of the Texas House of Representatives, introduced an April Fools resolution to illustrate how some of his colleagues didn’t read things they voted on. The bill passed in 1971, officially commending The Boston Strangler for his work in population control.
24. In 2014, as an April Fool’s joke, Audi advertised a car with a built-in rice cooker in Japan
25. Mattel made and sold Wonder Woman's “invisible jet” as a collectible. The package was an empty plastic shell with nothing inside and was originally intended as an April Fool's joke.