The four main actors all spoke Mandarin, but with different accents. Yun-Fat Chow had a Cantonese accent, Michelle Yeoh had a Malaysian/English accent, Ziyi Zhang had a Beijing accent, and Chen Chang had a Taiwanese accent. Because of the difficulty some Chinese-speaking markets had with the voices, some markets actually had a dubbed version (into standard Mandarin) of the soundtrack.
While Ziyi Zhang's character is obviously highly trained & skillful in martial arts, the actress herself has never had any official martial arts training at all. Instead she uses her dance techniques to learn her moves in these scenes, as if they were a dance rather than a fight (which in terms of creating & filming them is actually not that far from the truth).
The film is an adaptation of the fourth novel in a pentalogy, or five-novel cycle, known in China as the Crane/Iron Pentalogy and written by noted wuxia (kung-fu) novelist Du Lu Wang. The novels are "Crane Frightens Kunlun", "Precious Sword, Golden Hairpin", "Sword's Force, Pearl's Shine", "Crouching Tiger, Hidden Dragon", and "Iron Knight, Silver Vase". Much of the story is not about Li Mu Bai and Yu Shu Lien; they are in fact secondary characters who only become important later in the series. When a comic-book adaptation of the fourth book in the pentalogy was slated, illustrator Andy Seto re-watched the film to get inspiration for how to depict the fight scenes.
According to Yun-Fat Chow, he had to do 28 takes of his first scene on the first day of shooting because he had such difficulty speaking Mandarin. When asked in an interview with Time how he felt about his Mandarin pronunciation, he replied "It's awful".
Taiwanese-born Hong Kong actress Qi Shu was originally cast in Ziyi Zhang's role of Jen Yu and worked on the film for several weeks, until her agent pulled her from the movie to do a Pepsi commercial in Japan. (She has since changed agents!)
The film holds the record for the most Oscar nominations for a foreign film. It was nominated for 10 Oscars, including Best Picture, Best Director, Best Music (Song), Best Writing (Adapted Screenplay), Best Film Editing, and Best Costume Design.
Michelle Yeoh tore her ACL (anterior cruciate ligament) during the shooting of an early fighting sequence and had to be flown to the U.S. for knee surgery. She returned to the set at different times to film non-action scenes until the knee had recovered.
(at around 1h 5 mins) At the cave scene, Lo sings a song. This song is in one of old Turkish languages (probably Uyghur lang) which still can be understandable in today's Turkish language. Something along the lines of: "............... yiriliyorida, gordum su guzel kiz havar guni, .............. bu guzel aylari, ey guzel kiz havali kiz" As far as I understand, it means; "............. while she was singing softly, I saw that beautiful girl when sun goes down, ...................... this beautiful months, You beautiful girl, cool girl".
Michelle Yeoh did not speak Mandarin, and the script was presented to her phonetically with help from Mandarin-speaking crew members - her Malaysian accent can be heard throughout. Yun-Fat Chow did speak Mandarin (his first language is Cantonese) but native Mandarin speakers thought his accent strained and overdone.
The Green Destiny Sword Li Mu Bai carries translates to Green Dark World Sword - a place where the dead go. The Mu in Li Mu Bai's name translates to a kind of positive jealousy or longing - as in wanting something but probably never getting it.
(at around 15 mins) In the first night scene, Bo meets two night-watchmen who later give two knocks on clappers/rods, indicating that it was the 2nd watch of the night. The first watch begins at 7 p.m. and each watch is 2 hours long, so it was after 9 p.m when Jen first sneaks into Sir Te's residence. If we were shown how many times the night-watchmen then sounds the small cymbal/gong, we would know more precisely what time it was between 9-11 p.m.
According to old Taiwanese newspapers, in 1959 there was a Taiwanese-speaking movie called "Luo Xiao Hu and Yu Jiao Long," an earlier adaptation of Du Lu Wang's novel. The old newspapers noted that this version was also a martial arts film. The leading actress, Hsiao Yan-Chiou, was originally traditional Taiwanese opera actress. After this movie released, Hsiao married, leaving "Luo Xiao Hu and Yu Jiao Long" as her last movie. This movie is thought to be no longer in existence now, and it seems to hold no connection with Ang Lee's "Wo Hu Cang Long" except the adaptation source.
(at around 5 mins) The stamped documents shown by Shu Lien to the guards at the city-gate before she enters Beijing shows the date "In the 43rd year of the reign of (Emperor) Qianlong, the sixth month, the eighth day", which is the year A.D. 1778, somewhere in June or July.
Ang Lee comments that originally he did not wish for Shu Lien to wield the heavy two-handed straight sword against Jen. This is consistent within the movie, as Shu Lien indicates her preference of the 'dao', the saber with a broad, curved blade, instead of the straight-bladed 'jian', Li Mu Bai's weapon of choice. The Green Destiny is itself a jian.
(at around 3 mins) In the hall where Shu Lien first meets Li Mubai, there are two large sets of couplets hung on the wall behind them. The inner couplet reads "(Right) The Tall (Qiao) Tree spreads thousands of branches, but don't they have the same roots; (Left) the Long (Yangtse) River flows into tens of thousand of distributaries, but all have the same source" and is about maintaining harmony. The outer couplet reads "(Right) In Spring and Autumn sacrifices, follow the Ancient Sages' Rites and Customs; (Left) Arraying Left and Right, trace One Family's Generations of Continuity" and is about maintaining tradition.
The first draft of the screenplay said this: "You will note in the script that none of the fight scenes are described, and I will just inform you now that they will be the greatest fight scenes ever in the history of cinema, period."