I think any holiday that allows practical jokes is one to be wary of. I was especially bothered by these sites.
The WalYou.com site is especially dangerous, because it has annoying practical jokes you can play on other peoples' cellphones, digital cameras or work computers. Can you imagine how it would bug your fellow cubicle-dwellers to have their CAPS LOCK activated randomly? Or to fake them out with a phony Blue Screen of Death? These pranks make the old onion gum or squirting lapel flower seem benign by comparison.
If by chance you do work in an office and you were to try any of these pranks I couldn't stop you, could I? While I couldn't recommend you do any of these I would wash my hands of any complicity in guiding you to a website that provided these dirty tricks to you.
If you're curious about the true origin of this day this is probably as good (and concise) a place to start as any:
The History of April Fools' Day
By: Jennifer Maughan
Learn where this silly holiday originated with a brief history of April Fools' Day.
The idea of springtime practical joking and merriment has roots in ancient times. Many countries and cultures have long practiced some form of lighthearted celebration around the first of April. Practiced since 536 B.C., the prank tradition of Sizdah Bedar is still celebrated to mark the end of Persian new year festivities. The Jewish calendar marks Purim, a topsy-turvy carnival-like celebration with costumes and pranks. The ancient Romans marked March 25th by honoring the goddess Hilaria with a festival, filled with games and amusements. The Hindi calendar notes Holi, where one of the traditions is to paint friends and family with brightly colored pigment.
The origins of the April Fools' Day prank goes back to the late 1500s, when most of Europe changed from the Julian Calendar to the Gregorian Calendar. This calendar reform caused much confusion, and years passed before the new calendar system completely took hold. Someone who failed to note the switch was branded an April Fool, given that they were likely still celebrating the old new year holiday, held just after the time of the vernal equinox in late March. The new calendar moved the new year to January 1, but for years there was a small group of people who mistakenly celebrated on April 1. Of course, these traditionalists were made fun of; eventually jokes were played on them by sending them on fool's errands or tricking them into believing ridiculous things.
The idea of the All Fools' Day spread rapidly throughout Europe. In France, fools were called April fish, or "poisson d'avril," noting that it was just as easy to catch naïve young fish as it was to prank naïve people. Today's French children may tape a paper fish to the back of another and tease them until it is noticed. In Scotland, the gullible are the target of "Hunt the Gowk Day," where a "gowk" is a crazy or foolish person. Polish citizens avoid anything serious on that day and prepare various jokes and hoaxes. In the U.K, Australia, New Zealand and Zimbabwe, the April Fools' Day pranks and jokes must be done by noon on April 1, or the prankster will have bad luck.*There are a couple more Ripley's that, while not dated April 1, sure have the smell of practical joke to them. Do a guinea pig's eyes really fall out if you hold him by his tail? Can you really swim as fast in maple syrup as you can in water...and more importantly, why would you want to?
Here's a real joke! Click on the cover.