The Witness - S4-E23
Revealing mistake: As Schultz comes in the barracks door, there is a sliver of the studio background visible by the door jamb above his head.
The Witness - S4-E23
Continuity mistake: In the beginning, the guys are listening in on Klink's office. The cup in front of Newkirk has four pencils in it. The colors from left to right are yellow, red, blue, and orange. After the camera cuts to Hogan and Kinch, the wide shot shows five pencils arranged yellow, black, blue, red, and orange.
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