Ah, the traditional day of French class students tossing construction paper fish in the classroom and shouting merrily "Poisson d'Avril!"
An excellent explanation of the phenomenon:
And there you have it. I have played no tricks on anyone today, because, well, I used to be a big practical joker until I found out that if you jump out at Nate in the dark, in the library at closing while he is holding a MagLite, you will not be happy with the results.
Why do you have a fish on your back?
April Fools Day celebrations in France demonstrate the uniquely absurdist French sense of humour. It's customary to give your friends little chocolate fish. The classic April Fools Day prank is to stick a paper fish on someone's back. The unfortunate victim is then taunted with the phrase "Poisson d'Avril", or "April Fish".
Where did the celebration come from?
In late March the Romans honored the resurrection of Attis, son of the Great Mother Cybele, with the Hilaria celebration. This involved rejoicing and the donning of disguises. Hilaria means joyful celebration, and it is a word that has passed down to the English in the word hilarious, so these cheerful springtime celebrations have been with us for some time.
Where did the practical jokes originate?
A modern theory goes like this: In 1582 France became the first country to switch from the Julian to the Gregorian calendar established by the Council of Trent (1563). The New Year was moved from the end of March to January the 1st. Those who were unaware or disregarded the change and continued to celebrate the New Year between March 25th (Lady Day in England), and April the 1st, became the butt of various jokes.
But what about the fish???
This may have origins in the abundance of fish found in French rivers during early April after the young fish had just hatched. Much like March hares have a reputation for being mad, these Poisson d'Avril had a reputation for stupidity, being easy to fool with a hook and lure, so it was illegal to fish them. It may have become customary to fool people in celebration of the abundance of foolish fish.
On a brighter note, I have spent today researching the place I'm visiting tomorrow for interviews and catching up with contacts and picking out an outfit. Let no one say that I am unprepared for tomorrow.