The Three Musketeers (1973)

Continuity mistake: At one point D'Artagnan reaches the Duke of Buckingham, who is on a hunt. He has just killed a stag and his hands are covered in blood. D'Artagnan rides up and offers him a note from Queen Anne. He wipes his palms with a cloth before he takes the note, but his hands are still covered with blood up to and above the wrists. When he reads the note, he and D'Artagnan take off on foot for his castle where they go into a private room behind the walls. Suddenly it is apparent that his hands are perfectly clean right down to his scrubbed fingernails and, without explanation, the plot-heavy sequence continues.

Continuity mistake: When D'Artagnan skewers Jussac, his sword and victim are obviously between two hanging sheets of laundry. Cut to close-up, his sword is now stabbing Jussac through one of the sheets.

Continuity mistake: When D'artagnan follows the Landlord's Wife after their liason, and finds her in the street with the Duke of Buckingham, he drops to his knees to apologise for his rudeness, and we hear a splash to indicate he has just kneeled in a sizeable puddle. When the shot changes, he is still kneeling, and he is not kneeling in a puddle at all.

Trivia: Oliver Reed almost died when he was stabbed in the throat during filming of a swordfight scene.

Porthos: May one ask - delicately - the cause in which we're expected to die?
Aramis: When you go on a campaign, does the King give his reasons? He says, "Porthos, fight!" and you fight.
Porthos: Oh, I do, I do.
Aramis: Then let's go and be killed where we're told to! Is life worth so many questions?

M. Bonancieux: The Bastille! Well, I tell you, I don't want to go to the Bastille! Because it's got very deep dungeons and terrible instruments of torture operated by very unsympathetic men! And they snip very important parts off people.

D'Artagnan: Now, that man in his time has insulted me, broken my father's sword, had me clubbed to the ground, laid violent hands on the woman I love! He is inconvenient.

Question: Why was Cardinal Richelieu's costume changed from red to purple?