Two Nazis for the Price of One - S3-E17
Visible crew/equipment: A string is seen attached to Colonel Klink's cap that is used to yank off the cap after Colonel Mannheim fires his pistol at Klink.
How to Win Friends and Influence Nazis - S3-E7
Deliberate mistake: Burkhalter pulls some papers out of his bags marked "Top Secret." Why would German papers be marked in English, so the prisoners know what not to look at?
Nights in Shining Armor - S3-E8
Factual error: When the prisoners are in the workshop to "fix" the plumbing, sergeant Shultz is armed with a krag Jorgensen rifle. German soldiers were armed with the k98 mauser, not the krag.
Axis Annie - S3-E23
Continuity mistake: As Newkirk is talking to Axis Annie, his arms are crossed. They are uncrossed a second later without moving.
LeBeau and the Little Old Lady - S3-E25
Audio problem: After Hogan and company get into the car to go to town to get Lebeau, Klink is walking around to get in the passenger side, Schultz takes off, leaving Klink standing alone. After Klink calls out, you hear the screeching of tires sliding on pavement. Trouble is, the camp doesn't have any pavement.
Sticky Wicket Newkirk - S3-E20
Revealing mistake: When Hochstetter goes to open the window in Klink's office after the explosion rocks the camp, look at the background. You can see the studio lighting shining on the matte painting of the camp yard.
Plot hole: The prisoners fake a fire with some smoke bombs to have an excuse to rush into the print shop and smash up the print plates. Afterwards they even receive thanks and a reward for their valiant efforts. In reality, the guards would notice immediately that nothing in that room is even singed, but everything important has been smashed by fire axes.
Factual error: Erica says she has a plane to take Klink and her to Argentina. The only transatlantic airplane in Germany at that time was the FW-200 Condor, whose military value would have made it hard to requisition even for an SS Gruppenführer (which would be the real rank a "General" would hold in the SS, different mistake), let alone for his wife. Plus, even the FW-200 could not have made it even to the Brazilian coast without a refueling stop somewhere along the African west coast, which would have been a problem, because Germany had no possessions there. Klink, being a Luftwaffe (Air Force) officer, should have at least been suspicious of that plan, even if he didn't know all the details off the top of his head.
Everybody Loves a Snowman - S3-E14
Continuity mistake: Carter and Newkirk have just taken the escapees down the tree trunk to the tunnels. When they go to open it, they clear off the snow to open it. When the shot goes to a German soldier that was chasing them, the phony stump is suddenly covered over again. It would still have been visible, having just been exposed.
Other mistake: The scene in Klink's quarters is one of a few where you can see Larry Hovis' (Carter) wedding ring.
Continuity mistake: After Hogan, LeBeau, and Newkirk leave, Carter is sitting, holding the glass with both hands. After the cut, he's holding the glass in his right hand only.
Continuity mistake: After getting Crittendon to turn around, Hogan grabs his hat with his right hand. When the camera looks at Hogan, he's pulling his left hand back, holding his hat.
Some of Their Planes Are Missing - S3-E2
Visible crew/equipment: When LeBeau, Carter and Schultz enter the visiting Germans' quarters, when the door is open you can see the sound stage floorboards are uneven in front of the door to the neighbouring barracks.
Two Nazis for the Price of One - S3-E17
Continuity mistake: Freitag is shot at night, but when Hogan goes outside and talks to his men it's daytime.
Everybody Loves a Snowman - S3-E14
Revealing mistake: As the sink with the fake tunnel is prepared, just before Newkirk goes over to set things up, you can see movement through a crack in the door. It's Schultz, Hochstetter, and Klink, waiting their cue to enter.
Funny Thing Happened on the Way to London - S3-E5
Plot hole: When the driver of the car addresses Roberts (the real Roberts that is, not the double), Roberts reprimands him, telling him not to call him Baumann. It is safe to assume the guard was supposed to be speaking German, since he addressed Roberts by his German identity. That poses some interesting questions. Did Roberts speak English? In those days, most Germans did not even have a basic knowledge of the English language. Did he speak German? That would imply he has a good enough command of the German language to pass as a German. Roberts however isn't a spy like Hogan and his crew, but a pilot in the RAF.
Visible crew/equipment: After Hogan goes down into the tunnel in Klink's quarters, the stove moves back in place. As it does, the wire on the floor pulling the stove back in place is visible.
Factual error: While the show always made it winter time by having snow on everything (salt piles strewn about) and icicles on all the windows, this episode has an actual date of occurrence, June 6, 1944. They help to solve the snow on the set by taping the whole episode inside. However, the windows still all have the ice formations on them. It's late spring.
Factual error: The motorcycle courier coming in wears sunglasses that are definitely newer than 1942. Sunglasses with domed, wrap-around lenses were not invented in the 1940s.
Is There a Doctor in the House? - S3-E18
Continuity mistake: Hogan pulls a container with a red cross out of the drop box and opens it. It is labeled "penicillin" inside and contains among others several vials of clear liquid. Back in the camp, Hogan gives a box with a red cross on top to Kinchloe, saying "here's the penicillin." It is a completely different box.
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