On 1st April, many of you may be planning to be mischievous and play pranks on your friends and family.
That's because it's April Fools' Day, when we all get to play the joker!
"It has been celebrated in the UK since at least the 19th century," explains Andrea Livesey, a historian from the University of Bristol. "Children were commonly the victims of these pranks!"
So we wanted to find out more about why we celebrate April Fools' Day.
Andrea told us that not everybody agrees where the festival come from.
She says: "There is surprisingly little known about the origins of April Fools' Day and there are a large number of completely different - and quite entertaining - theories of its origin."
So let's have a look at some of them.
Theory 1 - Poetry
"Some have argued that a story told by early English poet Geoffrey Chaucer in the 14th century - where a fox plays a prank on a rooster (who is almost eaten because of it) - is the first reference to pranks taking place on the first of April."
The poet doesn't actually directly refer to April 1st though. In the poem, he says 32 days "syn March began", which people have said is "32 days since March began" which would be April 1st.
But those who don't believe this theory say he was just using confusing words to make fun of people in the poem.
Theory 2 - Calendars
Some believe the tradition started because of events in the calendar.
Something called renewal festivals date back to Roman times. These were a celebration at the start of a new year or season, when things went a bit topsy turvy.
"Servants could control masters or children could control their parents!" says Andrea.
March is the time of the Spring Equinox, so people think the joker tradition could come from this, as the beginning of spring and planting flowers was considered the start of the new year.
There is another calendar theory about when people started celebrating new year at the beginning of January, instead of the end of March.
Those who continued to celebrate it at the end of March, rather than on 1st January like we do today, were considered to be fools and had jokes played on them.
Theory 3 - Fishing in Europe
"The earliest concrete records we have about 1st April are from France and Holland in the 1500s and, because of this, people believe that it must have been a northern European tradition that spread to Britain," Andrea explains.
It is actually known as April Fish Day in some areas of Europe.
People think this is because there are a lot of fish in French streams and rivers around 1st April, and they are easy to catch - foolish fish!
So it soon became a tradition to play tricks on people on April 1st too.
"It is still a common trick in France, and elsewhere in Europe, to attach a paper fish to somebody's back on April Fools' Day, and also to give chocolate fish as gifts," Andrea says.
So it appears we don't actually know for sure where April Fools' Day officially started.
But one thing's for sure - people have been playing jokes on April 1st for a very long time!
So watch out that you don't get pranked!