Continuity mistake: Sgt. Schultz' serial number changes in every episode.
Continuity mistake: From time to time, Hogan's patch (reading COL. R. E. HOGAN) alternates from the lettering being faded, to the lettering being vibrant with the patch looking new.
Continuity mistake: Throughout the whole series, the guys access the tunnels through a trapdoor built into the bunk closest to what appears to be the east end of the barracks. What is interesting is the method used to make the trapdoor open and the bunk rise. sometimes, it's two taps, two slaps, or two pushes of a "key", a panel that's made to look like the side of the bunk.
Continuity mistake: Hogan is listed as being from different places throughout the series; e.g., Ohio, Bridgeport, Connecticut, Indianapolis, etc.
Continuity mistake: The scar on Burkhalter's right cheek changes location, relative to the mole on that cheek, in every episode. Possibly in every take.
Continuity mistake: The breast eagle on Schultz's uniform is sewn on backwards after the first season, and his belt buckle also changes from a Luftwaffe buckle to a different one.
Continuity mistake: Throughout the whole series, there are references to the building that houses Hogan and company. Sometimes it's Building 2, sometime it's Building 3. Also, there are times that Hogan's building has a direct view of the Commandant's building, and times when there is a building between them.
Continuity mistake: In the first episode, when seen from the inside, the door to the outside opens from the left. In the rest of the series the door opens from the right.
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