!!Poisson D'avril!!
(April Fish?)

Of course this is French for April Fools' Day, dating back to the 16th century when Charles IX, followed the Gregorian Calendar, decreed Jan 1st as New Year's Day, rather than April 1st (Solstice). Those who didn't follow the new calendar were called "fools" and sent invitations to fake parties and the like. French children fool their friends by taping a paper fish to their friends' backs - when discovered the child cries

"Poisson D'avril"

Why the connection to fish? Some believe that it's because the sun is leaving the zodiacal sign of Pisces at this time. Some think its because it was not permitted to fish at this time of year. Others say it's because some fish are pretty dumb and easy to catch!

This prank is a combination of the two - a fishy letterfold! I hope you enjoyed being fooled, and please, don't spoil it too soon for the others!

Here is the crease pattern (right-click on picture to "save as"), and the resulting fish-fold (same on both sides). Eyes and mouth can be added.