Request Permission to Escape - S1-E32
Continuity mistake: While Carter and Klink's secretary are conversing, the waste basket Carter holds switches positions from up to down and back again.
Request Permission to Escape - S1-E32
Character mistake: When ordering Schultz to finish cleaning his car, Klink salutes Schultz, his returning the salute with the garden hose in his hand leads to Klink being soaked. A salute is, except in rare circumstances, always initiated by the lower-ranking individual and returned by his superior, not the other way round. This rule is broken especially by Klink in several other places as well.
Request Permission to Escape - S1-E32
Other mistake: Carter is washing things in front of the barracks. There is snow on the ground and on the windowsills and they are wearing winter jackets but the cold weather doesn't bother him putting his hands in the water over and over. He even gets splashed in the face but it doesn't faze him.
Request Permission to Escape - S1-E32
Continuity mistake: As Schultz starts to wet Klink, several big spots appear on the left of Schultz's jacket, then disappear a moment later.
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