Jackie Chan doubled for Chikara Hashimoto for the scene where Chen kicks him out of the window. He took the kick and flew several feet. Bruce Lee immediately checked to see if he was okay. Chan played a guard Lee kills in Enter the Dragon (1973).
Bruce Lee openly admitted that in real-life, nunchaku versus the katana was actually an uneven match and should be avoided.
Sync sound was not widely used in Hong Kong cinema for a long time. The voices were dubbed even on the original Cantonese track.