Continuity mistake: When Klink goes to leave his quarters to meet the plane, he doesn't have his familiar outer coat in his arm or on him. When he gets to the rendezvous point, he has it on.
Other mistake: When the head counterfeiter comes in, there is a sign on the barracks behind him that says "BARRACK 3." Two problems with this. First, Hogan and company are housed in Barrack 3. Second, there is not a Barrack building between Hogan's building and Klink's office building.
Nights in Shining Armor - S3-E8
Other mistake: In the end, Schultz tests the faucets, and they work correctly. When Klink goes to touch the faucets, watch the drain. The high pressure jet of water comes from it just when Klink is over it.
Axis Annie - S3-E23
Continuity mistake: At dinner in the hotel, Hogan suggests a picture. Axis Annie agrees, and reaches down for the camera. After the shot cuts to a wide angle, she is reaching down again.
Factual error: While introducing himself to the downed Russian pilot, Hogan claims he is with the "US Air Force." He was actually with the United States Army Air Corps (USAAC) as the US Air Force wasn't formed until 1947, 2 years after the war ended.
Factual error: In this episode, the Royal Navy submarine that acts as a radio relay for Hogan's men is hunted by a destroyer. Like in most such Hollywood scenes, depth charges are seen exploding right next to the submarine, which just shrugs the blasts off. In reality, any depth charge that went off closer than 100 meters was instantly deadly to a submerged sub.
Sergeant Schultz Meets Mata Hari - S3-E4
Other mistake: As the lady Gestapo spy comes into the beer hall, Schultz not only has a matchbook in hand, but keeps looking at the action between the bartender and the lady, waiting for his entrance cue.
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