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.
Factual error: When Sally and Bryan are in the street, we can see, at their back, election posters. These posters appeared in 1932, one year after the movie is supposed to take place.
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.
Revealing mistake: Freeman Lowell has several cargo containers dumped off the spaceship, to make it appear the ship has suffered an accident. A wide shot shows the ship receding in the distance, with the containers rolling weightlessly in the foreground. As the foreground containers pass slightly in front of the more distant ones, they don't mask them; their images overlap. The containers were apparently composited into the shot with simple multiple exposures. (00:35:40)
Continuity mistake: During the opening credits, Peter Boyle is seen loading luggage into a red Ford convertible with a rear license plate reading 677 EIY. When he parks in front of the Community Legal Services office, the car's front license plate reads 185 ENV. A few moments later, when he goes to meet Robert Redford, the front plate reads 772 DYD.