Corrected entry: The whole story line is a plot hole. The blueprints would be a top secret item, and as such, wouldn't accompany the item they depict (in this case, missiles). Klink carries the prints around as if they were ordinary papers for no other purpose than to be "borrowed", copied, and returned by the Heroes. For this, Klink would have been eliminated.
Hogan's Heroes (1965)
1 corrected entry in season 5
Starring: Bob Crane, John Banner, Robert Clary, Werner Klemperer
Factual error: The German agent pretending to be an American pilot is wearing a one piece flying suit from the 1960's when he is questioned by Hogan and the British escapee in the barracks. It even has the US Air Force logo on the sleeve, which didn't come into use until 1947, after the war.
More quotes from Hogan's Heroes
Trivia: A sinister aspect of an otherwise lightheated comedy, but the fact is that Hogan and his men are war criminals. They engage in combat activities behind enemy lines when not in uniform, and worse, while wearing enemy uniforms. The Germans tried that during the Battle of the Bulge and those arrested were shot.
Question: Who was "Nimrod"?
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.
"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.
It's widespread enough that Wikipedia has an entire section on it: https://en.wikipedia.org/wiki/Nimrod#In_popular_culture
Correction: Not a plot hole. The rationale for the plans being present was probably because they were to be presented to the assembled general staff. That makes it a deus ex, not a mistake. It's often stated in the series how the Axis general staff considers Stalag 13 a particularly safe place, so there's no reason not to take top secret plans there. As a matter of fact, the safety is precisely the reason the demonstration is held in Stalag 13. As for the reason Klink carries the plans with him, that's not a proper plot hole either. Again, viewed from the German point of view, the plans were safe there, especially rolled up where nobody could peek at them. After all, no prisoner had ever escaped from Stalag 13. Fact is, the Germans have no clue that Hogan's men have ways to get those plans out of country. True, Klink probably shouldn't have put the plans down, but that's just his usual clumsy self, and as already pointed out twice, from his point of view he had no reason to suspect duplicity.
Doc ★