The meaning of "Z" : At the very end of the movie, a message tells us "Also the military regime banned (...) the letter "Z" which means "He is alive" in ancient Greek."
"Z" is tied with the Fritz Lang movie M (1931) for the record for shortest movie title ever. Holds the record for the movie with the shortest title to be nominated for the Academy Award for Best Picture.
In the French dialogue, the acronym CROC is expanded as "Combattants Royalistes de l'Occident Chrétien" ("Royalist Soldiers of the Christian West"). In the English subtitled version, the initials are preserved by changing the expansion to "Christian Royalist Organization against Communism".
The character of The Examining Magistrate (played by Jean-Louis Trintignant) is in reality Christos Sartzetakis - President of the Hellenic Republic (1985-1990).