So I figured I'd do a history of April Fools day, or All Fools day as it is called in some countries. Turns out that we aren't exactly sure what started it. The popular theory is that it came about because of the calendar change in France. Before the newfangled Gregorian calender they celebrated New Years on the 1st of April. When the calendar changed they moved it to Janurary 1st. Due to a lack of communication tools a lot of people didn't hear about this change, so they were labeled "fools" and people made fun of them. This turned into a day of making fun of fools and then was adopted by other countries.
However, England was already celebrating it and they didn't switch calendar systems until about 200 years later. There were already several other holidays around the time of April that involved pranking and having fun.
Whatever the origin is, there is no doubt that it's a day that many people enjoy and look forward to.