Aramis' statement, "I am a genius, not an engineer," is a pun in the original French ("Je suis un génie, pas un ingénieur").
Each of the four Musketeers are played by actors with different nationalities. Jeremy Irons is English, John Malkovich is American, Gérard Depardieu is French and Gabriel Byrne is Irish.
Anthony Hopkins was the first choice of Randall Wallace to play Aramis. He turned it down due to filming commitments with La máscara del Zorro (1998). Sam Neill and Alan Rickman were also considered for the role before Jeremy Irons accepted the part.
When Aramis (in his priest disguise) speaks Italian, the Italian dubbed version has him speaking Spanish instead.
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.