« Le premier avril » is a special day aimed at having fun. On this day, children make paper fish and try to tape it on their friend's back. When this trick is discovered, they yell « poisson d'avril ! ».
On TV and on the radio, journalists also make « poisson d'avril » with false informations presented in a funny way.
There are several explanations for this tradition, one of them is that France used to celebrate New Year's on the first of April until 1564 when King Charles IX decided that the year would begin on the first of January. For this special occasion, people exchanged presents. But some people disagreed with this change of day and refused to celebrate New Year's on the first of January. For this reason, some of their relatives started making fun of them offering them funny gifts and all kinds of silly presents.
Whatelse on this day ?
Nothing special really, no special meal so no special recipe ! Sorry.