In French-speaking April Fools’ customs, a paper fish may be stuck to someone’s back.
The prank is known as “poisson d’avril,” literally “April fish.” A child or prankster secretly attaches a fish, traditionally made of paper, to another person’s back. The victim may walk around unaware until someone notices it or the prank is revealed with the words “Poisson d’avril!”
The custom is especially associated with France and parts of the French-speaking world. Fish imagery appears in cards and decorations as well as in the practical joke. The exact origin is uncertain, despite popular theories connecting the tradition with calendar changes, Lent, fishing seasons and the zodiac sign Pisces.
This tradition should not be confused with the English expression “April Fool,” which usually describes the person fooled rather than the object attached. The paper fish is the distinctive French-language symbol.