Watch the Trains Go By - S4-E19
Visible crew/equipment: As Carter and Newkirk are caught by the wire, the shadow of the camera pulling back is seen on the ground.
Watch the Trains Go By - S4-E19
Visible crew/equipment: As Schultz stops the car, studio equipment is reflected in the windows.
Watch the Trains Go By - S4-E19
Visible crew/equipment: As Linkmeyer and Klink get in the car, a man in a white shirt can be seen moving around the camera position in the reflection on the car under her window.
Watch the Trains Go By - S4-E19
Visible crew/equipment: When Klink is by the fence acting busy and talking to Schultz, twice you can see the shadow of the camera on Klink's overcoat.
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