* ActingForTwo: Frank Finlay (Porthos) also played O'Reilly, the jeweler tasked by Buckingham to reproduce to two missing diamond studs.
* ActorInspiredElement: UsefulNotes/CardinalRichelieu says to d'Artagnan that he has no personal enemies, only enemies of France. This line is in neither the original novel, nor the script. Creator/CharltonHeston came across this quote of the Cardinal's when researching the role, and asked Creator/RichardLester to find a place to include it in the film.
* ActorSharedBackground: Anne of Austria was born in Spain and, being a member of the House of Habsburg, was actually Spanish royalty. Creator/GeraldineChaplin married a Spaniard, and her daughter, Creator/OonaChaplin, was born in Spain.
* AllStarCast: And how. The cast list is a who's-who of American and British stars of the 1970s. Creator/MichaelYork, Creator/OliverReed, Creator/RichardChamberlain, and Frank Finlay as the Musketeers, Creator/GeraldineChaplin as Queen Anne, Creator/JeanPierreCassel as Louis XIII, Creator/CharltonHeston as Richelieu, Creator/FayeDunaway as Milday, Creator/ChristopherLee as de Rochefort, Creator/RaquelWelch as Constance, Creator/GeorgesWilson as Tréville and Simon Ward as Buckingham. In total, the film's cast has a whopping 5 Oscar noms, 10 BAFTA noms, and 27 Golden Globe noms.
* BillingDisplacement: Despite playing the lead, Creator/MichaelYork is billed fourth. Creator/OliverReed gets first billing.
* CaliforniaDoubling: The movie(s) were shot in Spain and England.
* CastTheRunnerUp: Creator/CharltonHeston was originally offered the role of Athos.
* CreativeDifferences: In August 1973, Creator/RaquelWelch withdrew from the film due to creative and artistic differences. She announced she would instead make a film ''Decline and Fall of a Very Nice Lady''. However Welch wound up rejoining the film.
* CreatorKiller: An ''unintentional'' example: During the filming of ''The Return of the Musketeers'', Creator/RichardLester's longtime collaborative partner Creator/RoyKinnear fell off a horse and broke his pelvis. He died of a heart attack the next day. Lester grew so distraught that he quit making films, though he would make one last project, a concert film, for Music/PaulMcCartney two years following ''Return'''s release.
* DawsonCasting:
** Thirty-three year old Creator/RaquelWelch as twenty-two year old Constance Bonacieux.
** Thirty-nine year old Creator/RichardChamberlain as twenty-three year old Aramis.
** Thirty-one year old Michael York as eighteen year old D'Artagnan.
** Porthos was between Athos and Aramis in age, the former being thirty and the latter twenty-three. Frank Finlay was forty-seven.
** There is a certain level of ambiguity about Rochefort's age. He was either in his early or mid forties. Creator/ChristopherLee however was fifty-one making the former unlikely.
** Forty-one year old Jean-Pierre Cassel as twenty-four year old Louis XIII. Ironically, Louis only lived to be forty-one.
** Fifty year old Creator/CharltonHeston as forty year old Richelieu. This is at least justified, as the original novel points out that Richelieu is younger than he looks.
* DiedDuringProduction: Creator/RoyKinnear died from a horseback riding accident during filming of ''The Return of the Musketeers'' in 1988. His role was completed with a stand-in, filmed from the rear and with lines dubbed by a voice actor.
* ExecutiveMeddling: What was supposed to be a four-hour long epic became [[MovieMultipack split into two films]] because the producers didn't think that people would want to see a film that long. Since the actors were only paid the rate for one film, most of them sued and won. (This also directly affected ''Film/SupermanTheMovie'' and ''Film/SupermanII'' from the same producers, as they were also originally shot as one long production, though still separate films. Richard Lester replaced Creator/RichardDonner for ''Superman II''.)
** Richard Lester has said in interviews the producers cast Simon Ward and Raquel Welch. "Raquel is very big in all the small countries," said Ilya Salkind.
** The Salkinds refused to let Lester use any footage from the first two films when he was making ''The Return of the Musketeers''.
* FakeNationality:
** With the exception of Creator/JeanPierreCassel (Louis XIII), Georges Wilson (de Tréville), and Nicole Calfan (Kitty); none of the actors were actually French. Ironically, the three had [[SameLanguageDub their lines re-dubbed]] so their accents would match the rest of the cast.
** In ''The Return of the Musketeers'', the French Creator/PhilippeNoiret plays the Italian-born UsefulNotes/CardinalMazarin.
* FatalMethodActing: Creator/RoyKinnear died from complications of a broken pelvis after accidentally falling from his horse on the set of ''The Return of the Musketeers''.
* NoStuntDouble:
** Creator/RoyKinnear did his own riding stunts, as the production company could not find a stunt double.
** Creator/MichaelYork claimed that at one point he had to double for his own injured stunt double.
* OnSetInjury:
** Creator/MichaelYork had his leg cut in one duel and almost lost an eye in another. It got so bad that at one point, York remembers doubling for his injured stunt double. He later resorted to stuffing his script inside his clothes for protection.
** Creator/OliverReed was stabbed in the throat while filming the fight near the windmill and almost died. He also took a sword to the hand.
** Frank Finlay was struck in the face by a two-by-four, and burned in separate fight scenes.
** Creator/ChristopherLee fared better than most of the cast, getting off with just a sprained knee and a pulled shoulder muscle.
*** Lee did later recount, though, that he had to remind Reed during a sword fight that they weren't ''actually'' trying to kill each other.
** While filming their fight scene, Creator/FayeDunaway accidentally pushed Creator/RaquelWelch for real, causing her to fall and sprain her wrist.
* TheOtherMarty: Creator/KimCattrall was cast in ''The Return of the Musketeers'' at short notice because the original choice dropped out.
* PlayingAgainstType: Creator/CharltonHeston as Richelieu. He rarely played movie villains.
* TheProductionCurse: ''The Return of the Musketeers'': British character actor Creator/RoyKinnear died on set when a formerly placid horse he was riding, one thought suitable for the actor, became uncontrollably wild and galloped away, eventually bucking him off into a wall. He died a day later from complications to a broken pelvis. Kinnear's family successfully sued the film makers for negligence. Richard Lester was so shaken by the incident (he had worked many times with Kinnear and considered him a friend) that he retired prematurely from the film business, despite a series of successes.
* RecycledSet: The Duke of Buckingham's billiard room and the long hall behind it at his English estate is a leftover set from ''Film/{{Patton}}''. It is also seen in ''The Four Musketeers'', where Milady and Buckingham speak about American Indians and also serves as a set of rooms in ''The Return of the Musketeers'' for a different character in France some 10 years after the action of the first two films.
* RoleReprise: Creator/MichaelYork played D'Artagnan again in the 2004 MadeForTVMovie ''La Femme Musketeer''.
* SequelGap: 15 years between ''The Four Musketeers'' and ''Return of the Musketeers''.
* UncreditedRole: Creator/FrankThornton as a man in a small carriage.
* WhatCouldHaveBeen:
** Creator/RichardLester originally envisioned this as a film for Music/TheBeatles.
** Lester wanted Creator/MalcolmMcDowell to play d'Artagnan.
** Creator/AlanBates was the first choice for Athos.
** Creator/TimothyDalton and Creator/JonFinch turned down the role of Aramis.
** Creator/JulieChristie was considered for Constance in case Creator/RaquelWelch said no.
** When this was in its early stage of development, Creator/RichardBurton and Creator/UrsulaAndress were being pursued by the Salkinds.
** Charlton Heston was interested in returning as Cardinal Richelieu for the third film although the character had died between the novels. As a concession the film features a portrait of Heston as Richelieu which was gifted to Heston after the filming wrapped.
* YouLookFamiliar: Creator/JeanPierreCassel played King Louis XIII in the first two films and Cyrano de Bergerac in the third.
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