Alexandre Dumas, the author of the book for which this is based, adapted his novel on a historical account of a mysterious prisoner in the Bastille who was forced to wear a leather mask on special occasions for the two years between his imprisonment and subsequent death. The idea that he was a royal lookalike comes from a jest made by the historian Voltaire in the mid 18th century, about 70 years after the historical events.
In the book, the motives of Bishop Aramis are far less noble than those portrayed in the film. In the story, Aramis plots to replace Louis with Philippe as part of a master plan to have Philippe appoint Aramis as cardinal, and an eventual candidate for Pope. Aramis also has hopes to stack the Louis cabinet with allies leading to further power and a possible appointment of Aramis as prime minister.
Although Louis XIV, who was a real king, is a prominently featured character in the movie, the closing credits state that all characters are fictitious. This statement involves a loophole common to movies of this nature. The film portrayal diverges considerably from authentic descriptions of the real person, so the character is fictitious in the sense that the words and actions of the character are not claimed to be things that the real person said and did.
Even though Gabriel Byrne in the role of D'artagnan is supposed to be in character as much younger than the older Musketeers, Byrne, Jeremy Irons, and Gérard Depardieu are in fact almost the same age. Irons and Depardieu were both born in 1948. Byrne was born in 1950. John Malkovich was born in 1953 making him the actual youngest of the four men.
Some of the filming was done at the Château de Vaux-le-Vicomte, located in Maincy, near Melun, 55 kilometers (34 mi) southeast of Paris. It was built between 1658 and 1661, for Nicolas Fouquet, Marquis de Belle Île, Viscount of Melun and Vaux, the superintendent of finances of Louis XIV. Fouquet celebrated the completion of the château with a most extravagant feast, at which every guest was given a horse. King Louis however felt upstaged by the grandeur of the home, the event and suspecting that such magnificence could only be explained through Fouquet's pilfering the royal treasury, had d'Artagnan arrest Fouquet. d'Artagnan was assigned to guard him for four years until Fouquet was sentenced to life imprisonment. Soon after this, d'Artagnan was promoted to captain-lieutenant of the Musketeers.
The trivia items below may give away important plot points.
This film is one of the few, if not only film versions, that features the subplot of Louis XIV stealing Raoul's fiancée from him. The story plays out differently, however. Christine was originally Louise de la Valliere, a historical figure who was in fact Louis's mistress, and according to some document had previously been involved with a man called Bragelonne, on whom Raoul was based. In the book Louis does not send Raoul to Africa to be killed. He is instead sent to England on a diplomatic mission, and is recalled only when Louis's previous lover, Princess Henrietta Stuart (wife of his brother Philippe d'Orleans) calls him back. Raoul takes part in the conspiracy to replace Louis with Philippe (the twin), which ultimately fails. Sometime after this, he realizes that Louise loves Louis in return, and the heartbroken Raoul accepts a position with the King's cousin, Beaufort, in Africa, where he commits a kamikaze maneuver.
Although the book is often published under the title The Man in the Iron Mask, Philippe is not made to wear the mask throughout the book. Though he is imprisoned in the Bastille at the start, it is only after the failed attempt to supplant Louis with him that Louis gives the order to have his face covered.