Harpo Does Something Funny: In the finished screenplay, there were no details of what was happening in the action sequences. They would be written as 'They will be choreographed by Mr. Bruce Lee'.
Looping Lines: The entire movie was filmed without sound, and so virtually all the actors had to loop their dialogue after filming was complete, with a couple of exceptions:
Kien Shih (Mr. Han) spoke no English, so his voice was dubbed by veteran Chinese-American actor Keye Luke (of "Kung Fu", "Star Trek", "Gremlins", and "Charlie Chan" fame).
When the extended Cantonese/Mandarin versions were released for the first time in English in 1998, some extra dubbing had to be done, because no English dialogue existed at that time for those scenes. One of the scenes involved Roy Chiao (Shaolin Abbott) and Bruce Lee. Chiao was still alive (he died shortly thereafter), and was able to dub himself, but Lee's voice was supplied by Bruce Lee biographer John Little. Luckily, Lee's real voice was left alone for the scenes that originally used it.
The Other Marty: Jim Kelly replaced Rockne Tarkington, who quit the film three days before production was due to star because he thought the pay was too low.
Retroactive Recognition: Future martial arts stars Jackie Chan and Sammo Hung have small parts. Chan appears three times in the film. He is one of Su Lin's attackers (she knees him in the groin), and twice later, towards the end of the film in the big cave fight scene. Lee grabs his hair for a while before breaking his neck; he is also one of the stuntmen that Lee hits when he wields two sticks (according to Chan himself). Hung is Lee's sparring partner during the fight before the opening credits.
Unintentional Period Piece: The leisure suits, turtle necks, the funky music, Williams' afro and manner of speech along with mentioning that the Vietnam War was only a few years ago, all point to this movie being in The '70s. Also, this movie is mostly responsible for kick-starting the kung-fu craze in the US during this time.