According to the The Almanac Companion, a newsletter from the publisher of "The Old Farmer’s Almanac," the origin of April Fools' Day could go back to 16th-century France:

"At that time, New Year’s Day was March 25, with a full week of partying and exchanging gifts lasting until April 1. In 1582, the Gregorian calendar moved New Year’s Day back to January 1. Those who forgot or refused to honor the new calendar were the butts of jokes and ridicule."

What's the best April Fools' prank you've ever pulled?