Factual error: While the show always made it winter time by having snow on everything (salt piles strewn about) and icicles on all the windows, this episode has an actual date of occurrence, June 6, 1944. They help to solve the snow on the set by taping the whole episode inside. However, the windows still all have the ice formations on them. It's late spring.
Factual error: The motorcycle courier coming in wears sunglasses that are definitely newer than 1942. Sunglasses with domed, wrap-around lenses were not invented in the 1940s.
Nights in Shining Armor - S3-E8
Factual error: When the prisoners are in the workshop to "fix" the plumbing, sergeant Shultz is armed with a krag Jorgensen rifle. German soldiers were armed with the k98 mauser, not the krag.
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.
Factual error: On the map in Klink's office, the nearest town's name is Hamilburg. This a misspelling, as the real name is Hammelburg.
Factual error: The guard delivering the Russian captive in the tunnel at the start of the show has a paratrooper M1 carbine with a bayonet lug. Bayonet lugs were not attached to M1 carbines until after the war.
Factual error: Erica says she has a plane to take Klink and her to Argentina. The only transatlantic airplane in Germany at that time was the FW-200 Condor, whose military value would have made it hard to requisition even for an SS Gruppenführer (which would be the real rank a "General" would hold in the SS, different mistake), let alone for his wife. Plus, even the FW-200 could not have made it even to the Brazilian coast without a refueling stop somewhere along the African west coast, which would have been a problem, because Germany had no possessions there. Klink, being a Luftwaffe (Air Force) officer, should have at least been suspicious of that plan, even if he didn't know all the details off the top of his head.
Axis Annie - S3-E23
Factual error: After Carter realises Hogan got the envelope off so fast, Newkirk says "Speedy Gonzales." 'Hogan's Heroes' was supposed to take place from 1942 to the end of the war. Speedy Gonzales first appeared in "Cat Tails for Two" in 1953.
Factual error: Towards the end of the episode, Burkhalter gets a call from a General Seidenbaum. Anybody with such a "Jewish" name would have been weeded out of the officer corps by the Nazis. In fact, anyone of that name would have had great trouble even getting his Ariernachweis (proof or aryan ancestry), and without carrying a copy with him he could not have opened a charge account at the local bakery. Most people with such names (those who managed to pass the Nazi board of racial review) had them changed to more "German" ones like Müller or Schmidt to escape the constant bullying. A little bit of background on "jewish" names: At some time during the medieval period, Jews in the German Reich who traditionally didn't use last names were forced to have them. Many selected names like Gruenbaum, Cornfield, etc. Which over time were perceived as "typical Jewish" names, even though many bearers weren't even of Jewish faith any more.
Factual error: In this episode, the Royal Navy submarine that acts as a radio relay for Hogan's men is hunted by a destroyer. Like in most such Hollywood scenes, depth charges are seen exploding right next to the submarine, which just shrugs the blasts off. In reality, any depth charge that went off closer than 100 meters was instantly deadly to a submerged sub.
Factual error: In several episodes, Hogan's men communicate by radio with a British submarine, and the dialog hints that the sub is submerged at the time. During the WWII era, submarines could not communicate by radio without surfacing first. In most episodes one might argue that the sub could be running shallow with a mast up, which would perhaps be within the technical possibilities of the era, but in this episode, the sub is talking to Hogan's men while under attack by a destroyer. This pretty much rules out running at periscope depth, because ramming was regularly-used tactic for killing subs that were in the process of diving or surfacing. To avoid confusion: Nowadays, subs can communicate while running several hundred feet deep by using VLF and ELF. However, these are definitely not capable of transmitting voice, but are text-only.
Drums Along the Dusseldorf - S3-E30
Factual error: All through this episode, characters keep referring to the river the bridge *du jour* spans as "The Düsseldorf" or "Düsseldorf river." The city of Düsseldorf is situated on the river Rhine - there is no "Düsseldorf river." It's a well known fact that the producers were hardly geography whizzes, but not knowing the Rhine is bad even by their standards. Curiously enough, there kinda is a "Düsseldorf river" called the Düssel, and it meets the Rhine there. The Düssel however is a small streamlet that a well-trained man could probably jump over - so the mistake is still a valid one.
Answer: Nimrod's actual identity was never revealed in the series. It was only known that he was a British intelligence agent. Nimrod was not Colonel Klink. Hogan had only implied it was him as a ruse to get Klink returned as camp commandant, not wanting him replaced by someone more competent who would impede the Heroes war activities. The term "nimrod" is also slang for a nerdy, doofus type of person, though it's unclear why that was his code name.
raywest ★
"Nimrod" is originally a king and hero mentioned in the Tanach and taken into the Bible and the Koran. His name is often used in the sense of "stalker," "hunter," and sometimes figuratively as "womanizer" as in "hunter of women." I've never seen it used to denote a nerdy person, and although I cannot disprove that connotation, I think given his role, the traditional meaning is more likely the intended one.
Doc ★
It's widespread enough that Wikipedia has an entire section on it: https://en.wikipedia.org/wiki/Nimrod#In_popular_culture