Continuity mistake: When the Apes are trying to break into the mutant's church, Mendez looks towards the Alpha/Omega bomb, and is wearing a cream-colored jumpsuit with a purple sash. When the Apes do break in, his sash has disappeared. (01:25:50)
Factual error: During the scene where Clint Eastwood is trying to convince Don Rickles to join in the heist, there is a box of Almond Joy candy bars behind Don's head. They weren't introduced until 1946. (00:28:50)
Continuity mistake: Struck by Iris, Mrs. Hill falls to the ground (in obviously sped-up footage, incidentally) face up. As the Rev makes his unceremonious exit, she is lying on one side. (00:39:50)
Visible crew/equipment: When Mike and Susan prepare to start putting pieces of snow in the kettle, in the shot where Susan hands Mike the kettle, and he begins taking the lid off, the camera crew can be seen reflected on the kettle. (01:16:00)
Visible crew/equipment: When the police investigator is speaking with the man standing outside the store window and asks him if he would buy every tie in the store, in every close-up shot of the investigator, the reflection of the cameraman kneeling on the ground can be seen in his sunglasses. (01:08:25)
Continuity mistake: During Prince Rupert's first appearance, he greets his uncle King Charles I by doffing his hat and putting it back on. In the close-up shot he is holding his hat in place but in the wide shot his hand is on his side.
Deliberate mistake: When the family first entry Three Chimneys they have a single lamp as a light source. Entering from the door at the rear of the shot, everything in front of them should be in darkness to the viewer, but it's lit. Things in the background are lit even though there would be no line of sight to the light source. This is because lighting was added on set to allow the viewer to see things better, even though it ruined the realism.