The tiny cat drawn on the face of le Duc de Richelieu changes from his left cheek, to his right cheek, back to his left cheek, and back to his right cheek. This could be because the film was spliced backwards in some shots.
Richelieu is depicted as an effeminate homosexual. In fact, Richelieu was so notorious a ladies' man, Choderlos de Laclos based the character of Valmont in "Les liaisons dangereuses" on him.
Richelieu fell out of favor with Louis XV because he opposed Louis's mistress, Madame de Pompadour. Richelieu and Fabien would not have been at court at the same time.
Roulette began appearing at gambling houses in France in 1796, 22 years after the reign of Louis XV ended.
Noble Johnson's character is termed "An Apache," a French word which would imply he was a brutal pimp. That term did not come into use until the early 20th Century.