Best movie mistakes of 1972
Factual error: When Charles Bronson is making a telephone call on a pay phone, a 1971 or like vintage Mustang is parked within view...out of place for the time the film is supposed to take place. There are other similar auto related mistakes, mixing thirties cars with late models in traffic scenes.
Revealing mistake: When McDonald is in the tunnels and is called to pick up the phone, he picks up a red phone. It is a standard Bell TouchTone desk phone. To make the phone look more futuristic, there was no cord and it was disguised as a cordless phone. The port that the cord would plug into is covered by a piece of colored tape. This also can be seen in the operations center of Ape Control when the worker picks up the phone.
Continuity mistake: The protagonist is weilding his karate skills against the crooked cops in the final fight scene. One of his foes is wearing a white fishing cap. Superfly belts him and knocks of the cap, there is a cut and then the cap is on again. The cap is on and then off again twice more in the same fight scene.