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)
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.
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)
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)
Continuity mistake: When the police catches the pickpocketer at the beginning, they literally lift him off the ground. There is a close-up shot in between, and the lack of continuity is apparent in the hand position of the man. Not just that: vehicles obviously disappear and appear in every cut.
Visible crew/equipment: After telling the plumber to go the police station, the police investigator is inside his car, undoing his tie. There is a moment where he turns his head around to look out the back window. Here, the reflections of two people sitting in the back seat, one being the cameraman, the other, most likely the director, can be seen reflected in his sunglasses. (01:12:24)