Stupidity: The plans Hochstetter and Burkhalter find in Hilda's desk turn out to be for the Hindenburg, a large dirigible. Burkhalter says he never saw the plane (sic) they show before. The Hindenburg was a German propaganda icon and very well known to every child in Germany. It's nigh impossible a Luftwaffe (Air Force) general would not recognize plans of a dirigible when he saw them, or not know the Hindenburg. Note that despite everything, the plans from Hilda's desk are probably meant to be not the same ones Carter later says he found inside the boxes - A Luftwaffe general not recognizing the difference between a jet plane and a dirigible is even more stupid. To avoid unnecessary corrections: Yes, according to the boxes the kits aren't for the Hindenburg but for JU-87 Stuka bombers, but that's a different mistake and not relevant for this one.
Hogan's Heroes (1965)
1 stupidity in season 4
Starring: Bob Crane, John Banner, Robert Clary, Werner Klemperer
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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: What exactly is the "cooler"?
Answer: It's a solitary cell. Steve McQueen, star of 'The Great Escape' is known as the 'Cooler King'.