One theory says that it began in the 1500s when the Gregorian calendar took over from the Julian. Those who forgot the change and attempted to celebrate New Year's (previously celebrated on the 1st of April) on the wrong date were teased as "April fools."
Apparently there are a few rules: Pranking period ends at noon. It's bad luck to the perpetrator if any tricks are attempted after that time. Those who don't respond with good humor are said to attract bad luck. 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.
Does anyone have any good examples to share?
Here's some from Australia, who would be dumb enough to fall for these?
In 2003 newspapers in that country touted a breakthrough advertised by car-maker Mini that promised an end to parking hassles with its "vertical parking locator" and flagged the development of vertical parking lots on the sides of buildings. Not to be outdone, another paper's Good Living supplement featured a review of Species restaurant, where diners could feast on culinary delights crafted from animals featured on the World Wildlife Fund's endangered list. The restaurant, owned by April Phewell, specialised in braised slices of hairy nosed wombat, yellow spotted tree frog kebabs and Sumatran Rhino steaks. Two of the major dailies carried an advertisement that claimed motorists would be able to avoid road tolls through use of new technology that would render their vehicles invisible.