LeBeau has to get into the tank and run it because the control box has been removed, but after he gets out, the tank continues to maneuver although there is no one controlling it.
Carter is in the office dusting Klink's desk. He plants the phony letter on the desk and puts the entire stack of incoming mail on top of the phony letter. When Klink picks up the stack of letters, there is one letter under the phony letter that should not have been there.
During the introduction, the mini-tank rolls along and, after some bomb explosions, it rolls off the side of the road and stops (it may have hit some hidden part of the tree on the right, as the tree jiggles when the tank stops). When the tank stops, the antenna stays upright. Now the truck comes along and stops behind the tank. The civilian controlling the tank gets out of the back of the truck and runs to the tank (with the control box in hand). When he gets to the tank, the antenna is bent back, though nothing should have bent it back. During the close-ups, the antenna is bent back even further (until the Major straightens it up).
The tunnel to barracks 12 was just dug. And the krauts were sleeping in there. There is no way that there would already be a ladder and trap door into the building.
The gun in the tank fires several times, even though there is nobody to reload it, and it does not have an auto-feed mechanism. It is not stated what type of gun it is; from the looks of it, it could be a short-barreled 77mm field gun. Just the gun and the breach mechanism might be too much weight for the tank.
When the remote control tank begins firing its gun, the observers retreat - walking backwards. When the technician stumbles and falls backwards onto Klink's porch, it's clear that there is no bottom on the remote control box, and that the box is empty. The guts of the box are hanging down below, having simply fallen out.
Update: The bottom does seem to disappear for a few scenes, but reappears in the civilian's lap just before the tank runs into the General's vehicle. The confusion is because the box is rotated 180 degrees from its original orientation (when the group is shown just before the tank begins firing). The way the civilian was carrying the box before the firing begins, the box's antenna is to the civilian's right, but after the tank begins firing, the box is rotated 180 degrees, and now the antenna is switched to the civilian's left. If the original orientation had been maintained, the bottom of the box would have been facing the camera. The change in orientation puts the top of the box facing the camera - which has fallen out, along with the guts of the box. The bottom of the box is not visible as the group is retreating, but after the group falls onto the porch, just before the tank hits the General's car, the bottom reappears in the civilian's lap.
Update: The bottom does seem to disappear for a few scenes, but reappears in the civilian's lap just before the tank runs into the General's vehicle. The confusion is because the box is rotated 180 degrees from its original orientation (when the group is shown just before the tank begins firing). The way the civilian was carrying the box before the firing begins, the box's antenna is to the civilian's right, but after the tank begins firing, the box is rotated 180 degrees, and now the antenna is switched to the civilian's left. If the original orientation had been maintained, the bottom of the box would have been facing the camera. The change in orientation puts the top of the box facing the camera - which has fallen out, along with the guts of the box. The bottom of the box is not visible as the group is retreating, but after the group falls onto the porch, just before the tank hits the General's car, the bottom reappears in the civilian's lap.
Sgt. Kinchloe calls Colonel Hogan "General", while he is giving an update about the pictures of the tank. Update: Kinchloe does address Colonel Hogan as 'Colonel'. The line is, "The pictures of the tank came out fine, Colonel." (Closed-captioning also indicates the use of 'Colonel'.)
When the remote control tank fires, its barrel is level and the explosions occur behind the group of Germans which means the missiles would have passed through the group of Germans yet they suffer no injury.
When the mini-tank is first brought into Stalag 13, there are obvious track marks in the ground to the left of the truck as it comes thought the gate - so this scene of the tank being brought into Stalag 13 was shot out of sequence.
In some of the outdoor scenes by the front gate, electrical poles and wires are in the background. These are the power service lines to the residential neighborhood on the other side of the berm.
The opening in the floor of building 12 would not have been perfectly crafted and have a handle on it, since it was a quick-and-dirty access tunnel. The building is obviously a general use building that has been fitted out as the workroom for the tank, but has served as a barracks or a storeroom in other situations.
The truck that is driven into camp has its steering wheel on the right side, indicating that it is of British manufacture. Trucks on the continent and in Germany in particular would have their steering wheels on the left.
While Hogan is dictating the phony memo, he walks around the table. As he turns the corner closest to the camera, a white flash, caused by a film anomaly on the master, appears for a frame or two behind Hogan's head.
One of the prisoner 'extras' in the background in the barracks is wearing Air Force enlisted chevrons, 3 wings angled down with a circled star in the center. The Air Force chevrons first appeared in March 1948 after the United States Air Force became a separate service.
When Colonel Klink is speaking with Hogan in the Commandant's office, one of the studio lights is seen reflected in Klink's monocle numerous times.
When the German major checks the tank out before the tests, LeBeau is already in the tank. If he had done a decent check, he would have found LeBeau in the tank and found that the control box was missing.
When the truck is seen on the road, it does not have a trailer. When the tank is brought into STALAG 13, it is on a trailer. Nothing is said where the trailer came from. Update: This is irrelevant. By the time the tank is brought into the camp, more than 24 hours have elapsed since Newkirk first saw it (when it broke down). Since the truck had already been in camp at least once (when Klink met with the Major and the civilian), it is logical that the trailer could have been 'borrowed' from Stalag 13, or any other nearby military installation. It is also quite possible that the trailer was broken down and kept in the truck for just such a situation - but was not visible. Either option is plausible, since they would not have been able to get the tank onto the trailer without fixing it first, and that would explain the delay in getting the tank to Stalag 13.
When LeBeau is inside the tank controlling it, he is steering it based on the 'commands' that Hogan shouts to him. However, there is no way that he would be able to hear those 'commands' over the sound of the tank's engine and tracks.
In the introduction, when Newkirk returns to Stalag 13, Schultz is on patrol. Newkirk, about to go in the tunnel (in the stump), sees Schultz and backs off. Schultz says he's out of gas and sits on the tunnel stump. He then pulls out a pack of cigarettes, pulls a cigarette out and puts it in his mouth. While Schultz is doing all this, Newkirk walks out from behind the trees and pulls his lighter out of his pocket - preparing to light the cigarette. However, from the angle Newkirk approaches Schultz (and based on Schultz's size), there is no way Newkirk could have seen Schultz pull out the pack of cigarettes, get one out, and put it in his mouth - so he would not have known to get his lighter out when he did.
When Carter installs the bomb in the mini-tank, he looks for a place to put it, then shoves it into what appears to be the barrel of the gun, but that is blocked with a plug - as seen when LeBeau is driving the tank.
In the denouement, Klink tells Hogan that he intends to win that prize. However, Hogan theoretically doesn't know that there is a prize at all. Hogan suggested to Klink that, after the beautification project, Berlin should give him some kind of award or cash prize, and Klink said he would suggest it - discreetly. However, Klink never tells Hogan that the suggestion came to fruition. This is obvious when Hogan asks Klink how working around the clock to beautify the camp will help pay for Burkhalter's car. In order to keep Klink from suspecting something, Hogan should have acted more surprised that there was a prize at all.