Plot hole: The boys take out the radio control unit from the mini tank. Le Beau is needed to get in and drive it to make it appear okay. After going between the buildings, they get him out, and start it on its way. Trouble is, no remote control and no driver, yet it turns and operates smoothly.
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.
Revealing mistake: As Hogan goes through the hole to the ladder, the "rock" he brushes against flexes for a second. Likewise, when Kinch climbs through, the "rock" under his hand flexes and mashes down as his weight is on it.
Factual error: In the very end, Klink comes up to the boys. As he stands beside Hogan, the Desilu Studios Water Tower is present behind them.
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