Revealing mistake: As the spy troupe prepares to leave by airplane, a Kübelwagen with soldiers comes up, which Burton shoots with his MP40. As the car bursts into flames, the driver and passengers are revealed as dummies, since no one could or would sit around quietly while they were on fire.
Continuity mistake: The car that Schaffer and Smith are riding in with the Germans is launched in the air by hitting a pile of snow and then comes to a sudden stop by hitting a pile of gravel where the Germans are killed. What happened to the pile of snow when Schaffer and Smith push the car backwards?
Revealing mistake: When the Allies are dropped from the plane into the snow and they find the dead soldier. Watch close, because the dead soldier blinks his eyes...
Continuity mistake: After Smith and Schaeffer are done rigging the trees and poles with explosives, Schaeffer gets off the motorcycle and you can see the seat of his pants is wet. As they are entering the shed, the seat of his pants is now dry.
Character mistake: The adjutant who wakens Major Wilhelm Wilner to tell him he has a phone call from the Schloss Adler has no breast eagle on his tunic. (01:27:40)
Revealing mistake: After Smith and Schaffer are captured and while they are being transported by car, Schaffer pushes one of the guards out of the car and a struggle begins which causes the car to crash. After the crash, the body of the guard that was pushed out of the car magically appears about 50 feet behind the accident (just before the crash there was no body). (00:49:25)
Factual error: As the coach moves through the village near the end of the film, it drives past a tracked vehicle. The vehicle is a Hotchkiss LPz, a type of armoured personnel carrier not produced until the 1960s.
Plot hole: When Smith and Shaffer take the gondola up to the castle, they step down on the roof of the car with heavy steps. It is completely unrealistic that the Germans inside did not hear them.
Continuity mistake: When Smith and Schaffer intrude on Carnaby's interrogation, the Gestapo officer and Mary are having drinks in the café, where he makes a statement that might reveal a fault in her identity (a location in Dusseldorf). Her hand is fixed on her chin, but the next cut shows her hand fully on her cheek.
Continuity mistake: As Mary is starting the rappel down the rope out of the castle, her MP-40 is slung on her right side with the muzzle pointing forward, but in the next shot it is slung across her back with the muzzle pointing to her left. (01:55:55)
Factual error: When Lt. Schaffer is sneaking up on the German soldier, in the radio room in the castle, you see and hear the soldier changing radio station channels. Most of the music you hear playing on the radio is distinctly a 1960s style easy listening music and not 1940s music.
Factual error: Smith has the books with names in his pocket when he goes into the water, jumping from the cable car. When he shows the books to Turner, they are in perfect shape. They should have been waterlogged or at least showed some sign of water damage.
Continuity mistake: Major Smith (Richard Burton) forces one of the traitors out of the castle window on a rope. He is wearing standard battle dress. When the traitor is shot by one of the Germans, he falls wearing a camouflage smock.
Plot hole: When Smith and Schaffer are entering the castle via a rope Mary has lowered for them, Smith stops halfway up to look through a large window. Clearly visible through this window are the faces of at least two soldiers with others in the background. It is inconceivable that not one of them would notice: A) the rope suddenly dangling outside; B) Smith's solid frame as he stares in at them; C) Schaffer scrambling up the rope after Smith; or D) the rope bouncing around while Schaffer drags it in along with the attached backpack. (01:10:00)
Continuity mistake: In the scene where the group parachutes in, the sky is cloudy and we can see snowfall, but watch carefully, as the men make their way to the equipment containers and then to find Sgt Harod we constantly see shots switching between cloudy and snowfall, then to no snowfall and sometimes sunlight, then back to cloudy and snowfall again. This switch back and forth is even more evident on the closeups of Richard Burton.
Plot hole: In one scene, the heroes of the film (i.e. Burton, Eastwood and others) locked themselves up in the cable car control room within the castle. The pursuing Germans wasted valuable time trying to break down the heavy wooden door of the control room with axes. Why didn't the Germans use grenades or other explosives? They could have instantly blown open even the sturdiest wooden door.
Visible crew/equipment: In the scene where the Germans are pursuing Richard Burton's escaping party as they make their way towards the aircraft waiting for them, you will see the first of two pursuing German Kubelwagons being hit with machine gun fire and flipping. When this happens, you will see a cable used to flip the vehicle on the bottom left side of the screen being quickly retracted as it becomes detached from the Kubelwagon's axle.
Factual error: Schaffer and Smith are captured and the Nazis are taking them away in a car. After some fighting, the car crashes. While the Nazis fly through the vehicle's windshield, our heroes sit like they had seatbelts, which they didn't.
Continuity mistake: In the scene where they all jump from the sky tram into the water after escaping from the castle, we see the blonde woman (Mary) swim to shore. As she gets out, her hair is absolutely soaked and matted to her head. When the angle of the camera changes, we see her only this time, he hair is almost perfect and only slightly damp and is actually blowing in the soft breeze.
Continuity mistake: When Burton and Eastwood jump from the cable car into the river, Burton jumps before Eastwood. However, the next shot downward has the Eastwood stuntman landing in the river first with the Burton stuntman still above him. We know it's Burton because of the bandaged hand. (02:06:15)
Answer: When the guard comes in, Burton explains what's going on. Also he is dressed as a German officer so his explanation and actions are plausible.