Continuity mistake: After Hogan leaves the airman in the tree, LeBeau jumps down, and looks up to tell the man it will be OK. When the camera looks at the man, you see LeBeau's legs and feet behind him.
Visible crew/equipment: As the General gets in his staff car and it leaves, the film crew and equipment are reflected on the sides.
Audio problem: The top of the coffee pot is on the basket rather than open, but we can hear the conversation.
Continuity mistake: As the general comes into Klink's office, Carter pours another cup of coffee, and starts to put the pot down. A second later, he's putting it down again.
Continuity mistake: During Carter's second meal, the napkin in his shirt comes loose and starts to fall. A second later, it's firmly in place in his shirt.
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