Fish of April!

April Fools' Day is surprisingly universal. The custom of playing pranks on the first of April is widespread in Europe, in places like France, Italy, Poland, and the United Kingdom, whose inhabitants carried it with them to the places they colonized around the world. Iranians do the same on the 13th day of their year, which is usually the first or second of April in the Gregorian calendar. Spanish-speaking areas celebrate a similar holiday in the last few days of December.

April Fools' Day is also one of the few things celebrated consistently on the internet, a place with no unified geography, language, cultural or religious traditions. Being generally run and populated by people whose sense of humor runs strongly towards the "ha ha only serious" end of the spectrum, the internet thinks that April Fools' Day jokes are hilarious beyond belief, and spend a fair amount of time and effort making them as awesomely tongue-in-cheek as possible. These range from the traditional spoof RFCs (since the internet has no actual governing body, only people who choose to cooperate in order to keep things running, RFCs, or Requests For Comments, are how new proposals are floated to the technical powerhouses behind the network) to elaborately planned and produced mock ad campaigns from newcomers like Google, who's put up more than one contribution this year. [Edit: Ooh, and a third!]

Every so often, somebody hits upon an April Fools' joke so successful, it lives on in online myth forever. In 1984, for example, a single posting on Usenet that purported to be from a gateway in the Kremlin kicked off one of the most infamous pranks in internet history. The world was still rather busy with the Cold War, and even in the United States where the distributed network technology originated, most of the sites on the internet belonged to universities or megalithic research corporations. Being able to talk to the notoriously paranoid and security-conscious Russians over a telnet connection was unheard of. Perhaps even more astonishing is the fact that the first real Soviet gateway came online only six years later, while the government of the USSR was still in the process of disintegrating.

More recently, a wide variety of companies with an online presence have gotten into the act, although to minimize the chance that someone will mistake fun for reality, they tend to make their pranks so outrageous that most of the humor comes from their absolutely serious presentation. and teamed up in 2009, for instance, to offer $99 flights to Mars. That page is still an active one on their server, although moved into an out of the way subdirectory. It's not unusual for the prank pages to be preserved in perpetuity -- the people who work on these are usually quite proud of them.

The Brits are for some reason much better sports about being April fish than much of the rest of the world. As a general rule, they provide thorough and approving coverage of a lot of the pranks, such as YouTube's entry for last year. Some of their most respected media outlets have also been the origin of many of the most infamous jokes, such as the Guardian's multi-page fold out travelogue on the island of San Serrife, and one of the most famous hoaxes of all time, the BBC's 1957 report on the spaghetti trees of Swizerland.