The movie is originally in French and sets in Montreal, a francophone city. However, many of the English speaking actors in this movie were dubbed by French actors instead of Quebec-born actors. This made quite an uneasy reaction to moviegoers at the release, as many found annoying the "Parisian French" used in the movie, compared to the "Montreal French" accent which would have been more appropriate for this production.
Lino Ventura and Edouard Carpentier were good friends in life. Ventura and Carpentier started in pro wrestling in France and were stunt men for fight scenes in the 50s (especially with actor Eddy Constantine). Ventura went on to acting and Carpentier moved to Canada to continue his successful pro wrestling career.
That's the only time in his career that Lino Ventura kisses a woman on the lips. No one knows if Angie Dickinson improvised and took him by surprise. Ventura was a very puritan husband, regarding of his beloved wife Odette. But gossips told long after his death that he had a relationship off screen with another lady.