He made him an April fool

April Fools' Day is celebrated in different countries on April 1 every year. Sometimes referred to as All Fools' Day, April 1 is not a national holiday, but is widely recognized and celebrated as a day when many people play all kinds of jokes and foolishness. The day is marked by the commission of good-humoured or otherwise funny jokes, hoaxes, and other practical jokes of varying sophistication on friends, family members, teachers, neighbors, work associates, etc.

In France and Italy children (and adults, when appropriate) traditionally tack paper fish on each other's back as a trick and shout "april fish!" in their local language ("poisson d'avril!" and "pesce d'aprile!" in French and Italian respectively).

In Holland April fool’s is closely linked to the fact that on 1st of April 1572 the Dutch rebels against the King of Spain, the Watergeuzen, captured the town of Brielle in the  province of South-Holland, a seminal event in the formation of the Netherlands .