It has become tradition on the first of April to pull jokes of the harmless variety on those near and dear to us. We plot and we scheme, and often the yuks are funnier in our imaginings than how they play out in reality, but that doesn’t stop us from sending the little kid in us out on a rampage. Even the most staid among us have been known to indulge in a practical joke or two, so beware of trusting anyone on that day.

How the custom of pranking on April 1 came about remains shrouded in mystery.

When the western world employed the Julian calendar, years began on March 25. Festivals marking the start of the New Year were celebrated on the first day of April because March 25 fell during Holy Week. The adoption of the Gregorian calendar during the 1500s moved the New Year to January 1. According to the most widely-believed origin postulated for April Fools’ Day, those who could be tricked into believing April 1 was still the proper day to celebrate the New Year earned the sobriquet of April fools. To this end, French peasants would unexpectedly drop in on neighbors on that day in a effort to confuse them into thinking they were receiving a New Year’s call. Out of that one jape supposedly grew the tradition of testing the patience of family and friends.

But that’s only one theory. Others are:

The timing of this day of pranks seems to be related to the arrival of spring, when nature “fools” mankind with fickle weather, according to the Encyclopedia of Religion and the Encyclopedia Britannica .

and the . The Country Diary of Garden Lore , which chronicles the goings-on in an English garden, says that April Fools’ Day “is thought to commemorate the fruitless mission of the rook (the European crow), who was sent out in search of land from Noah’s flood-encircled ark.”

, which chronicles the goings-on in an English garden, says that April Fools’ Day “is thought to commemorate the fruitless mission of the rook (the European crow), who was sent out in search of land from Noah’s flood-encircled ark.” Others theorize it may have something to do with the Vernal Equinox.

Some think to tie in with the Romans’ end-of-winter celebration, Hilaria, and the end of the Celtic new year festival.

Wherever and whenever the custom began, it has since evolved its own lore and set of unofficial rules. Superstition has it that the pranking period expires at noon on the 1st of April and any jokes attempted after that time will call bad luck down onto the head of the perpetrator. Additionally, those who fail to respond with good humor to tricks played upon them are said to attract bad luck to themselves.

Not all superstitions about the day are negative, though — fellas fooled by a pretty girl are said to be fated to end up married to her, or at least enjoy a healthy friendship with the lass.

In Scotland, an April fool is called an April “gowk” — Scottish for cuckoo, an emblem of simpletons. In England, a fool is called a gob, gawby or gobby. In France, the victim of a hoax is called a “poisson d’avril,” an April fish. (“April fish” refers to a young fish, thus one easily caught.) The French delight in shouting “Poisson d’Avril!” at the denouement of the foolery. Some also insist all such pranks include a fish or at least a vague reference to same within the joke. Asking someone during a phone conversation to hold the line, then later returning to the call and inquiring of the victim if there’d been any bites is a popular groaner. So are pranks which trick the victim into placing calls to fish shops or the local aquarium.

The media can’t resist getting into the act. Radio personalities are especially drawn to creating playful hoaxes. The year Canada introduced a two-dollar coin, pranksters from CHEZ FM fooled listeners into believing April 1 was the last day the treasury would honor all the two-dollar bills still in circulation. Local banks and the Royal Canadian Mint fielded call after call from concerned citizens. That same year, other radio pranksters had people going through their pocket change in search of the elusive two-dollar coins which had mistakenly been minted from real gold.

It’s not just the DJs who give into the urge to prank on April Fools’. Canadian Member of Parliament Sheila Copps was responsible for a particularly creative leg-pull in 1996. On the respected news show CBO Morning, she announced that the clock in Ottawa’s Peace Tower was being switched over to digital.

Arguably the best media-generated April fools’ joke dates from a Richard Dimbleby “news report” aired on 1 April 1957 on BBC’s Panorama. It opened with a line about Spring coming early that year, prompting the spaghetti harvest in Switzerland to be early, too.

Against a video backdrop of happy peasant women harvesting spaghetti from trees, whimsical claims about the foodstuff’s cultivation were made in a straightfaced manner. Spaghetti’s oddly uniform length was explained as the result of years of dedicated cultivation. The ravenous spaghetti weevil which had wreaked havoc with harvests of years past had been conquered, said the report.

More than 250 viewers jammed the BBC switchboard after the hoax aired, most of them calling in with serious inquiries about the piece — where could they go to watch the harvesting operation? Could they buy spaghetti plants themselves? (For those anxious to try their hand at homegrown pasta, Panorama producer Michael Peacock offered this helpful hint: “Many British enthusiasts have had admirable results from planting a small tin of spaghetti in tomato sauce.”)

Although adults get into the spirit of things (ask any zoo worker about manning the phones on April 1 and having to field endless calls for Mr. Lyon, Guy Rilla, and Albert Ross), it’s the children that seem to truly celebrate the day with wild abandon. April Fools’ pranking between students and teachers is an ongoing battle of wits, with kids favoring the timeworn standards of a tack on the chair, the “missing class” (kids hide under their desks when the teacher is momentarily called out of the room), or a springy fabric snake coiled in a can of nuts. Not every teacher fights back, but those who do are often inventive about it. For more than 20 years, one grade school teacher in Boston comes in early on that day to write the day’s assignment upside down on the blackboard. When her curious students arrive, she tells them she did it by standing on the ceiling.

The style of April Fools’ pranks has changed over the years. Sending the unsuspecting on pointless errands was an especially prized practical joke in those earlier post-Julian days. In modern times, that form of pranking has shifted away from April Fools’ merriment and seemingly become a rite of initiation into many groups, both formal and informal. New campers are routinely sent on a mission to retrieve the left-handed smoke shifter from its last borrower by more experienced campers who then quietly guffaw to themselves as the tenderfoot wanders about in vain on his quest. Others are often roped in to add to the hilarity, with each person the newcomer asks pointing him in towards yet someone else who will further the joke. Rookie pilots are sent in search of a bucket of prop wash, and new carnies sent on wild goose chases for the elusive keys to the fairgrounds.

Current tastes seem to run more to funny phone calls and media-driven extravaganzas. But it’s still okay to reach back to older times for inspiration. Be a traditionalist — on April 1 send a co-worker to fetch a tube of elbow grease or 50 feet of shoreline.