April Fools' Day, a day marked by the commission of practical jokes, gags and hoaxes played on unknowing friends and relatives -- is a longstanding tradition of delight and vexation for all those involved.  

Although the origin of the day is obscure, one theory is that the term April Fool was coined for those who signaled the first day of spring early after the adoption of the Gregorian Calendar in the year 1582. There is also speculation it originated after King Charles IX changed the first day of the year from April 1 to Jan. 1. Those who didn't get it were called April Fools and taunted by villagers.

In Canada, the jokes only traditionally last until noon. After that, the trickster is labeled an April Fool. In French-speaking ares of the country, the annual tradition includes poisson d-avril -- translated as "April's fish" -- where pranksters attempt to attach a paper fish to the victim's back without them noticing.

In other countries like Ireland, France and the U.S., the jokes continue until midnight, much to the chagrin of those who are fooled.

The tradition of April Fooling is longstanding in the world of media. Perhaps the most notable television hoax of all time is a 1957 BBC television segment in which farmers can be seen harvesting a bumper crop of spaghetti, resulting from the "virtual disappearance of the spaghetti weevil."

The three minute spoof, which was filmed outside a Swiss hotel, prompted hundreds of phone calls to the station to question the story's validity, or to ask about how they could grow their own spaghetti trees (BBC producers told them to "place a sprig of spaghetti in a tin of tomato sauce and hope for the best").

Here are some of the most notable April Fools' pranks from around the world, pulled off to varying degrees of success:

  • The left-handed Whopper: In 1998, Burger King ran a print ad saying customers could buy a left-handed burger where the condiments were designed to fall out of the right side. Result? People not only requested the new menu item, but demanded the old one back.
  • Taco "Liberty" Bell: Fast food giant Taco Bell bought a full-page ad in The New York Times saying they had purchased the U.S. Liberty Bell to "reduce the country's debt" and renamed it the Taco Liberty Bell. 
  • Changing the value of pi: In 1998, the newsletter of New Mexicans for Science and Reason had an article saying the Alabama legislature had voted to change the mathematical constant pi to the "Biblical value" of 3.0.
  • Killing the mayor: A pair of local Chicago radio DJs reported its mayor Thomas Menino had been killed in a car accident. Lending credence to the prank was that the mayor was on a flight, and could not be contacted. Result? The pair of hosts was fired.
  • Game show switcheroo: An April Fools' Day 1997, television game show hosts Alex Trebek and Pat Sajak switched hosting duties on their shows Jeopardy! And Wheel of Fortune. Letter-turner Vanna White played as a contestant.
  • Google mind control: In 2000, Google revealed a new technology called MentalPlex, which could read a user's mind to determine a search query before he even touched the keypad. No surprise, all of the results were Fools' Day related.

And the best highlights of 2009 (so far):

  • YouTube turns its videos upside down
  • UK paper The Guardian promises to publish exclusively in 140-character tweets
  • Amazon is making clouds
  • Google mail service Gmail launches an AutoPilot feature that analyzes your personal messages and responds all by itself
  • A Vancouver/>/> sports radio station announces retired NHL right-winger Pavel Bure would sign with the Vancouver Canucks for the upcoming playoffs