The Informer - S1-E1
Other mistake: Klink has on his monocle, as usual. If you look closely, the monocle is a single lens, with no frame. From Episode 2 onward, the monocle has a frame and a gallery. Also, Klink wears it at an angle, not unlike the Penguin in the original Batman series, who also wore a monocle without a frame.
Other mistake: After Shultz herds the prisoners into the barracks, Hogan opens the door and motions to Newkirk in the tank to get going. Problem is, there are no side viewports for Newkirk to see Hogan, and it looks like he motions to the camera. Also, Shultz is at the wrong end of the building to see the tank go into the end of the barracks.
The Late Inspector General - S1-E4
Other mistake: While the General is in Klink's office making the recommendation for Klink to be commandant of all German POW camps, he mistakenly calls Stalag 13, Camp 13 three different times. Camp 13 was referenced in the black and white pilot episode.
Suggested correction: Stalag is short for "Stammlager." "Lager" is the German word for "camp." (To avoid unnecessary discussions: depending on the context, "Lager" can also mean stash, cache, storage, warehouse, bedding or bearing, but in this context it is indubitably to be translated as camp). So "Camp 13" is absolutely correct in this context.
The Flight of the Valkyrie - S1-E5
Other mistake: As Crittendon pops through the wall, it is easily seen that the wall is Styrofoam, or other similar easily moldable material.
Go Light on the Heavy Water - S1-E9
Other mistake: After the smoke bomb goes off in Klink's office, there is a shot from the outside where the boys get a blanket to catch Klink. If you look at the window of the office behind them, you can see the smoke coming out in an up and down pattern, suggesting the smoke to be coming from a rig controlled by an out-of-sight crew member.
Top Hat, White Tie and Bomb Sights - S1-E10
Other mistake: When Klink is trying to demonstrate the automated gates to Burkhalter, Kinch makes the gates close, knocking Klink into Burkhalter. Before Klink tells Schultz to open the gates, they are already in motion.
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.
Oil for the Lamps of Hogan - S1-E14
Other mistake: Anytime Hogan steals one of Klink's cigars from the back of the humidor, he takes the hinge pin out from the left of the box (camera's right). This time, he takes out the pin, got the cigar, and put the pin back in from just what looked like just left (camera's right) of center.
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.
Other mistake: The truck was stashed behind Hogan's barracks. The Kommandant's office was on the other side of the building. While stealing the boxes of gold, there would be no way that the POWs would have been able to see any approaching figure.
Other mistake: After the truck is stopped, Newkirk tosses a dart at the tyre in order to flatten it. Since the tyre hit was the rear tire, there should have been the track from the front tire, but wasn't. Also, a puny, hand-tossed dart couldn't have penetrated the thick construction of a heavy-duty truck tire, let alone flatten it in twenty seconds.
Other mistake: When stopping the truck and Schultz, the area directly behind Carter and LeBeau can be seen to be a matte painting. The reason is because where they are is completely covered in snow, but the open area is very little, and there is a huge snowdrift piled up at the wall.
The 43rd, a Moving Story - S1-E23
Other mistake: When Hogan uses the water barrel periscope to spot Manor Kuhn, the first shot is from an impossible angle.
I Look Better in Basic Black - S1-E28
Other mistake: When Hogan asked the girls if they wanted to try to escape to England, the one in "basic black" said that anything is better than being booked in a German prison camp for three years. How did she know when the war would be over?
Request Permission to Escape - S1-E32
Other mistake: Carter is washing things in front of the barracks. There is snow on the ground and on the windowsills and they are wearing winter jackets but the cold weather doesn't bother him putting his hands in the water over and over. He even gets splashed in the face but it doesn't faze him.