Jean-Louis Trintignant's character is named Simon Duroc. In the actor's previous movie with this director, the celebrated Un homme et une femme (1966), his character was named Jean-Louis Duroc.
When Jean-Louis Trintignant's character is being grilled, the policeman mentions that witnesses saw a man and a woman. Trintignant responds by whistling a bit of the theme from his previous movie with Claude Lelouche, the international sensation Un homme et une femme (1966).
Towards the end of the sequence, early in the film, where Simon is trying on various disguises in the photo booth, there's a single frame closeup of Trintignant making a silly face.