The Flame Grows Higher - S1-E31
Visible crew/equipment: Toward the end of the episode, after the two women are taken out by the Gestapo, Shultz, Hogan, Lebeau, and Newkirk are standing having a drink. The camera goes in for a close-up on Shultz, there is a noticeable shadow of the camera on Shultz's coat, and right arm.
The Flame Grows Higher - S1-E31
Revealing mistake: As Hogan, Le Beau, and Newkirk help Schultz up the slope to the "forest fire", there is lumber stacked across a low spot in the top of the bank and covered with "snow" and grass. Probably meant as a path.
The Flame Grows Higher - S1-E31
Continuity mistake: At the end, as Schultz and Hogan come out of the office, there is a blank wall, like a kind of foyer. Any shots of the front door from the inside show the door opens directly into the outer office of the secretary.
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