When Seymour is talking with the prostitute, her scarf moves from one shoulder to the other in alternate shots.
Frank walks into Detective Fink's office, sits down and lights a cigarette. The cigarette remains in his mouth until a close-up shot, where it is missing. When the wide shot is resumed, the cigarette is back again.
The exterior location scenes of Mushnick's Florist shop clearly show that the business located there is the Good News Rescue Mission.
Mel Welles's character name is spelled as "Mushnik" in the end credits, but appears as "Mushnick" on the sign outside his shop.
Jackie Joseph's character name appears to be spelled incorrectly as "Audry" in the end credits. On the sign outside of Mushnick's shop advertising the new plant, the name appears as "Audrey" Junior, the spelling most often used for this name.
When Wilbur Force (Jack Nicholson's character) walks through a door to see the dentist, he says "Is this doctor's office?" and the audio is off.