The Great Impersonation - S1-E21
Plot hole: This episode revolves around training the reluctant, untalented Schultz to impersonate Klink to get the captured heroes back from the Gestapo. This is actually a pretty common theme, somebody, usually one of the heroes, impersonating an officer to free a prisoner. The plot gives no reason why this time, they would have to use the cowardly, untalented Schultz instead of doing it themselves.
The Flame Grows Higher - S1-E31
Revealing mistake: As Hogan, Le Beau, and Newkirk help Schultz up the slope to the "forest fire", there is lumber stacked across a low spot in the top of the bank and covered with "snow" and grass. Probably meant as a path.
Continuity mistake: When Schultz comes out, he talks to the guard posted there. A moment later, the guard is gone.
Other mistake: The wooden steps in front of the office look to be one plank measuring 3" by 18", but in the collapse under Klink, they appear to be two pieces. Also, Le Beau sawed through the middle support, but neither Schultz or Klink step on it.
Revealing mistake: As Klink steps off the porch of his office, in the long shot you can tell it is his stunt double.
German Bridge Is Falling Down - S1-E7
Character mistake: When counting the prisoners right at the beginning of the episode, Schultz counts to 15. However, including Hogan there are 19 men in formation.
German Bridge Is Falling Down - S1-E7
Continuity mistake: When we see the men lighting cigarettes, there are 25 people forming the arrow. When we are treated to an aerial view of it, there are 37 dots of light visible.
German Bridge Is Falling Down - S1-E7
Plot hole: We see Hogan's men empty out the gunpowder from a lot of cartridges inside the armoury. What did they do with their empties? It's not like a mound of empty cartridge cases on the ground wouldn't draw some suspicion is it? Yes, I am aware some options come to mind, e.g. putting the bullets back in and stuffing them back into the belts, but none of that is actually shown or talked about - LeBeau even chucks one cartridge over his shoulder, implying they are not very concerned about hiding their tracks.
Happy Birthday, Adolf - S1-E17
Character mistake: The artillery officer asks "Does headquarters expect a squad of infantry to replace experienced artillery men?" Hogan only offered "his detachment", and he's wearing a Luftwaffe uniform (and so is LeBeau). Why does the artillery officer get the idea that the "detachment" would be infantry, that is to say, ground forces (Heer) troops? To avoid confusion: Yes, the Luftwaffe did have infantry units, but those would be viewed by other branches as Luftwaffe guards primarily, not as infantry.
Kommandant of the Year - S1-E3
Factual error: A sharp brass cone has been put over the spike on Klink's Pickelhaube, so Hogan can pin the page torn from the Geneva Convention onto it. The real spike of a Pickelhaube has concave slopes, and it isn't pointy enough to pin a piece of paper onto it.
Audio problem: Hogan knocks out his pipe against the Prussian helmet on Klink's desk. It makes a tinny, metallic sound. The Prussian Pickelhaube was made from compressed leather, not metal.
Continuity mistake: LeBeau and Newkirk are on a building roof and the Nazi flag is blowing in the wind with great force. In the next shot a guard tower is shown with a Nazi flag that's hanging straight down and not blowing at all. (00:01:00)
The 43rd, a Moving Story - S1-E23
Revealing mistake: As Carter and Newkirk sit by the wall catching their breath, a seam can be seen running vertically where two wall sections meet behind them.
Request Permission to Escape - S1-E32
Continuity mistake: As Schultz starts to wet Klink, several big spots appear on the left of Schultz's jacket, then disappear a moment later.
How to Cook a German Goose by Radar - S1-E24
Continuity mistake: As Tillman starts to talk to Hogan, he places his hand on, then removes, it from, Hogan's arm. A second later, he repeats removing his hand.
Other mistake: After talking to the officers in the Höfbräu, the scene shifts to a closed business with Hogan talking to the waitress. As it shifts, the cameraman accidentally shakes the camera.
Continuity mistake: When Newkirk calls "Heil Hitler", everyone in the lobby salutes. A second later, in the closeup of Hogan and Newkirk, everyone's arms are suddenly back by their sides, much too quickly to be real.
The Safecracker Suite - S1-E27
Continuity mistake: After saying "I hate to be a killjoy", Newkirk has his fork up and pointed towards Kinchloe. A second later, it's pointed down.
Anchors Aweigh, Men of Stalag 13 - S1-E16
Audio problem: As the last German soldier before Hogan goes up the ramp, Le Beau is heard saying "schnell, schnell!" (fast, fast). As he says it, his mouth doesn't move.
Anchors Aweigh, Men of Stalag 13 - S1-E16
Continuity mistake: After saying that Michaels disappeared, truck and all, Klink brings his hands together, and interlaces his fingers. A second later, the fingers interlace again.
Answer: It's a comedy, not a documentary.
stiiggy
Perhaps it was counterfeit. There are numerous episodes where they deal in counterfeit monies.