As Chen makes his way through the Japanese school at the end of the movie he cautiously goes to open the sliding doors by using one hand and standing to the side. Upon opening the door the scene cuts to the other side and he is suddenly standing centrally and opens both doors together. This happens more than once.
The "Magic Pants" goof. Bruce Lee enters the Japanese Karate school for the first time carrying the framed and glass-covered "Dung Ya Bing Fu" sign. A fight between Bruce and the entire dojo breaks out. As he whirls around fighting his waist sash loosens and his kung fu pants sag deeply, revealing about three inches of white underwear from the back. Then a sudden cut shows Bruce posing motionless having defeated the current round of Japanese attackers. His pants? Tied up around the waist, nice and snug. Now that's some kung fu!