On lui a fait un poisson d’avril = They made him an April fool.
Je suis comme un poisson sur la paille = I am like a fish out of water.
Polichinelle
C’est le secret de Polichinelle = It is an open secret; Every one knows it.
Il a avalé la pratique de Polichinelle = He is very hoarse.
[La pratique de Polichinelle is the squeaker that a Punch-and-Judy man puts in his mouth during a performance.]
Politesse
*Force politesse, trop de finesse = Full of courtesy, full of craft.
Pont
Il se porte comme le Pont Neuf = He is in splendid health.