Robert De Niro and Michelle Pfeiffer appeared in Stardust (2007), New Year's Eve (2011), and The Wizard of Lies (2017).
When John D'Leo first met Dianna Agron on-set, he unknowingly asked her if she was the Make-up Girl. Agron burst out laughing and said "I'm your sister!"
Giovanni (Robert De Niro) is invited to talk about the movie Goodfellas (1990) at a special screening. De Niro starred in that movie, with the two movies also sharing several supporting cast members.
The book on which this film is based on had a sequel, Malavita Again, published in 2008.
When Don Luchese (Stan Carp) receives the bucket of ice in prison, he is reading the newspaper "La Repubblica". In the top right corner of the front page a picture of "LEON" can be seen, and next to it advertisement for "NIKITA". Both films made by Luc Besson: La Femme Nikita (1990) and Léon: The Professional (1994).
After beating up the plumber, Robert De Niro's character quotes a line by Al Capone: "You can get further with a kind word and a gun, than you can with just a kind word." This same line is said by De Niro when he played Al Capone in The Untouchables (1987).
The film makes unconventional use of English subtitles for the French dialogue. Instead of traditionally being displayed at the bottom of the screen, the text appears next to, or above the speaker.
Albeit as an Executive Producer, this is the first time Martin Scorsese has worked with Robert De Niro on a feature film since Shark Tale (2004).
The first Luc Besson film to be shot with anamorphic lenses since Léon: The Professional (1994). All of his later films had been shot with spherical lenses in Super 35, but he decided to go back to anamorphic for this film, and surprised Cinematographer Thierry Arbogast when he told him so.
The Paris SG trading cards show the names Charlie Clerc and Stéphane Robuchon, members of the film's Art Department.
Fred Blake/Giovanni Manzoni (Robert De Niro) says that he needs a psychiatrist. This is a nod to De Niro's roles in Analyze This (1999) and Analyze That (2002).
When Fred Blake/Giovanni Manzoni (Robert De Niro) begins writing his novel, his voice-over is heard over black and white stock footage of Rudolph Valentino's funeral, including a shot of Adolph Zukor, Douglas Fairbanks, Sr., Charlie Chaplin, and other famous film artists as the pallbearers.
The school attended by Belle and Warren is the "lycée Jules Vallès" (i.e. Jules Vallès High School). Jules Vallès was a French journalist and writer during the nineteenth century. There is no real "lycée Jules Vallès". The school, "collège Jean Moulin in Gacé", was transformed into the school for the film.
When Giovanni starts writing his book, and old black and white reels are showing, at one point, there is a shot of former Swedish world champion boxer Ingemar Johansson sitting at the table.
Features TommyLee Jones and Michelle Pfeiffer, both of whom played Batman villains. Two Face and Catwoman, respectively.