Audio problem: As the baby tank runs by the group in a wide shot, you see Hogan's mouth moving in a conversation, but the words don't match up.
Audio problem: The top of the coffee pot is on the basket rather than open, but we can hear the conversation.
Audio problem: After Schultz discovers the boys in the cannon plant, Hogan lifts a cannon up and taps the metal inside. If you watch closely, he only taps three times, but there are four tap sounds.
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