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.
The Kamikazes Are Coming - S6-E20
Revealing mistake: As the rocket blasts out of the recreation hall, the guide wires for the model are visible.
Factual error: The first episode of Hogan's Heroes (Season 1) begins with a view of Stalag 13 and a title: "Germany, 1942." That said, Colonel Hogan indicates in several episodes that he has worked in the Pentagon although construction of the Pentagon was actually completed in 1943.
The Kamikazes Are Coming - S6-E20
Other mistake: As Marya comes out of camp office, the seams between the sections of the studio flooring are visible at the bottom of the shot.
Klink for the Defense - S6-E19
Visible crew/equipment: As Newkirk and Hogan enter the office, the shadow of the boom mike plays on the wall.
That's No Lady, That's My Spy - S6-E17
Other mistake: The Kommandant's building and the barracks appear to be only twenty to twenty-five feet apart, showing that this scene of Roll Call is in the studio. Otherwise, the outdoor shots are at the studio back lot.
Revealing mistake: In the close ups, Professor Bauer's spectacles do not have lenses.
Revealing mistake: As the truck passes Carter and Newkirk, it's easy to tell they're hiding behind tarp-covered boxes rather than the greenery or rocks around them.
Other mistake: As Schultz talks to Burkhalter, it sounds like he says Captain.
Visible crew/equipment: As Schultz calls for attention, the studio lighting is reflected in his monocle.
Factual error: As the staff car comes up the street, there are a number of neon signs lit up, as well as store fronts. This is wrong as during the night in wartime Europe, such lighting would be dark to avoid night bombing.
Other mistake: As Hogan and Kinchloe sit on the bunk to keep the trap door from opening, the secret switch to activate it is visible.
Continuity mistake: The whole operation is supposed to be at night, but when the original seven approach the gate to surrender, it's late afternoon, and very light.
Happy Birthday, Dear Hogan - S4-E26
Other mistake: Hogan returns to camp after meeting with the underground, after learning the Germans are setting a trap. Kinch went down in the tunnel to Radio London just before Hogan returned. Hogan asked the men, "Where's Kinch?" and he shouldn't send any messages. Since Kinch was in the tunnel, Hogan should have seen or heard Kinch in the tunnel using the radio. (00:07:50 - 00:10:45)
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.
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.
Other mistake: Hogan is disarming a booby trap briefcase. The bomb expert tells him over the radio he has to decide to turn the handle clockwise or counterclockwise. The expert doesn't know which way to turn it. Hogan turns the handle counterclockwise and disarms the booby trap, and the expert says counterclockwise. There's no way the expert would have known which way Hogan turned the handle. (00:21:50 - 00:22:26)
Factual error: While introducing himself to the downed Russian pilot, Hogan claims he is with the "US Air Force." He was actually with the United States Army Air Corps (USAAC) as the US Air Force wasn't formed until 1947, 2 years after the war ended.
Oil for the Lamps of Hogan - S1-E14
Plot hole: The Heroes take an empty oil drum to the depot, knowing full well that Schulz will protest, allowing them to steal a full one. However, all but their barrel have snow on it. Since it's really salt, it all falls off as they load it on the cart. With real snow, that wouldn't happen. It would be quite obvious that the barrel they are taking out is not the one they brought in.
Plot hole: Five minutes into the show, Klink and Hogan are in Klink's office when a gestapo major comes in. When Hogan leaves, Klink mentions Hogan's name and the major realises with surprise that that is Hogan and then says he knows all about Hogan and his description. That alone should have led the major to know that this was Hogan. Hogan also has his name on a tag on his jacket.