Bruce Lee wasn't actually meant to be in this movie. He was only there doing action choreography as a favor to long-time friend, Little Unicorn. The enterprising producers filmed Bruce Lee working, and edited the footage into the movie. Lee was reportedly less than impressed.
In 1972, Bruce Lee's star was rising faster than anybody could have imagined. In the midst of all this, Little Unicorn, Lee's long time friend and confidant was offered a leading role. Lee offered assistance to the man who helped him get back into the Hong Kong movie business. The result was this movie, the only movie outside of his own that Bruce Lee action-directed and helped promote. Apart from Unicorn, there are many co-stars from Lee's movies also in this one.
"One of These Days" by Pink Floyd is featured in this movie.