When the door falls on Zeke, his hands are near the top of the door, but in the next shot they've changed position.
When Dan draws his pistol and prepares to threaten Ms. Miller after she lets out D.C., the camera cuts away from Dan, and we hear the "ka-CHUNK" sound of the pistol's slide being racked to chamber a round; however, when Dan subsequently approaches her, the pistol's hammer isn't cocked. If Dan had racked the slide, the hammer should be cocked unless he had manually decocked it when the camera cut away, which seems like a highly unlikely thing to do while threatening someone.
The FBI agent takes a paw print off the mark on his forehead, not directly from D.C. This would reverse the print.
In the beginning of the movie it shows that the girls each have a bedroom on the second floor. But when Patti is showing agent Kelso Ingrid's room as a place he can set up in, he comments about usually having a room on the second floor so as not to be disturbed.
After FBI Agent Zeke Kelso got D.C.'s paw prints, D.C. should still have ink on his feet. However, D.C. doesn't leave any paw prints on the laundry hamper he steps on before he jumps out the window, escaping.
In the beginning of the film, after D.C. pulled down Gregory Benson's duck from the string, the fishing line that was used to pull down the duck can be seen.
When Margaret Mitchell took off her watch to scratch HELP on the back, then put around D.C.'s neck, the metal on the back of her wristwatch is almost as weak as aluminum foil, and too easy to make a mark with a knife blade, in ten seconds of "H-E~".
After D.C. jumped out of the window after being paw printed, Zeke Kelso applies the paper to his forehead. For one, the print on his forehead is crooked, but when it is seen on the paper, it is perfectly straight. Also there was a second paw print right beside copied one, which should have left some kind of a mark on the paper.
Toward the end of the film, Gregory's Mercedes was parked directly in front of Zeke's car in front of the Randall house, however, when Zeke and Ingrid drive away, he pulls straight forward out of camera range, which makes it impossible for Gregory's car to be there.
When kidnapped bank teller Margaret Miller is begging with the crooks not to kill her, Grayson Hall calls Frank Gorshin's character, Iggy, by the name of Neville Brand's character, Dan.
At the drive-in, on Thursday evening, when D.C. is playing with the butterfly, for a brief moment the fishing line holding the butterfly up can be seen above D.C.
After FBI Agent, Cahill accidentally walked into some empty tin cans, that made a loud noise, this scared D.C. D.C. quickly runs away to hide, below a fence. Then D.C. is up at the top of the same fence-line, not holding on to it by the claws, inside its paws. Apparently, D.C. was lifted up to the fence-line, by someone off-screen.
As clearly evidenced by the numerous scenes in which D.C. makes a rear-view retreat from the camera..."it" (D. C. them diabolically clever felines) keeps changing sexes.
Dan's Colt Commander pistol has an external hammer that must be cocked for the pistol to fire. However, when D.C. scratches at the door and Dan opens it to investigate, his pistol isn't cocked; this is a remarkably foolish move for a seemingly seasoned gunman, as a prowler outside the door could have wrestled the gun away before Dan could cock it.
Mrs. Tabin claims she's bringing Margaret some vegetable soup but judging by the color of the broth, it is chicken noodle soup.