Everyone Has a Brother-in-Law - S2-E23
Factual error: Schulz repeatedly calls Klink's adjutant "Kapitän." In the German armed forces the rank Kapitän only exists in the Navy, the German equivalent for the American rank of Captain (which is obviously meant here) is Hauptmann or Stabshauptmann.
Everyone Has a Brother-in-Law - S2-E23
Other mistake: When the boys are listening on the coffee pot, the red light to indicate power is not lit.
Everyone Has a Brother-in-Law - S2-E23
Continuity mistake: Hogan is reading the note from the underground on the clipboard that Newkirk brought in. When done reading, Hogan is holding the board at waist height. In the close up, it's suddenly chest height.
Answer: It's a solitary cell. Steve McQueen, star of 'The Great Escape' is known as the 'Cooler King'.