Bruce Lee actually struck Jackie Chan in the face with one of his fighting sticks. Chan admitted that it was his own fault: he wasn't where the fight choreography required him to be, and would have been fine if he'd been on his mark. In any case, Lee was so horrified that he immediately helped Jackie up and hugged him while apologizing profusely, and later insisted that Chan could work on all of his movies after that. Unfortunately, Lee died before he could keep his promise, but Chan still claimed the moment was one of the greatest things that has happened to him in his entire career (he even admitted that he hammed up how much pain he was in because he didn't want Lee to stop hugging him).
The movie was made for $850,000, and took in over $90 million worldwide at the box office.
An extra challenged Bruce Lee to a fight to see if he really was that good. Lee won the fight and sent the extra back to work.
Shih Kien was a close friend of Bruce Lee's father since they both worked in Cantonese Opera business. Kien worked as a makeup artist and Bruce's father as an actor. Their relationship was so close that Bruce addressed Kien as "uncle" and Kien called Bruce "nephew". During a break, Bruce got a premonition and said to Kien, "Uncle, I feel that you will live longer than me." Surprised to hear that, Kien then replied, "Nephew, don't force yourself too hard. You are overworking yourself." Bruce died one week before Enter the Dragon was released in Hong Kong.
Jackie Chan: Appears twice in the film. Towards the end of the movie 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), and then falls into a pit of acid.