The Safecracker Suite - S1-E27
Continuity mistake: While Klink is talking to Hogan and the Major, the chair next to the door is almost centered under a picture frame. When the Major is arrested the chair is moved to the left. When Klink sits down, the chair is centered again. (00:03:50)
The Safecracker Suite - S1-E27
Continuity mistake: As Günther leaves the room, Klink touches his forehead and begins to sit down (or his knees are buckling, not relevant). After the next cut, he sinks down into a chair in a closeup. That same chair was behind Hogan before the cut.
The Safecracker Suite - S1-E27
Continuity mistake: As Schultz is asking about Alfie, saying "Who captured him, the Kaiser?", Hogan's hands are down. A second later, his chin is in his right hand.
The Safecracker Suite - S1-E27
Continuity mistake: After saying "I hate to be a killjoy", Newkirk has his fork up and pointed towards Kinchloe. A second later, it's pointed down.
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