Revealing mistake: When the truck with Hogan and company pulls up to the Luftwaffe HQ, the camera pans to the right to look at Klink getting out of the side car. When the camera cuts back to Hogan and company, they shake as if the truck just stopped, but it can be seen that the truck was stationary.
Revealing mistake: When Schultz is on the way out after giving the guys the news about the inspections and roll calls, you can plainly see that the background behind him is a matte painting. This is easy to spot because the building in the distance is lighter in color, and there are ripples in the fabric used.
Revealing mistake: When the guys are by the half-track keeping Shultz busy, if you look just above and to the left of Shultz's head, you see some tall fencing at the top of the hill in the distance. From the set up, if appears to be a baseball field outside of the studio property.
Revealing mistake: When the men are in the yard during their exercise period playing football, there is a wide shot of the yard. The half-track is to the left of the screen with Shultz next to it. If you look above the barracks, the Desilu water tower and a large metal building, possibly a studio building, can be seen.
Revealing mistake: Toward the end of the episode, a guard is watching Helga posing in a one piece bikini for Lebeau. As you look past him, you see only blue screen, no view of the surrounding property. Same when Hogan climbs up, you don't see the tops of buildings; you can tell it's on a soundstage.
Revealing mistake: After Hogan and the boys decide to get rid of Tillman, they "accidentally" set fire to the trash can on the Kommandant's porch. To that end they load up a bunch of trash that's been soaked in gas. Then Hogan tosses a lit match in it. The fire starts at the bottom, but all of gas soaked stuff, and the match, were at the top.
Revealing mistake: When the boys set the trash can on fire in front of Klink's office, there is a problem with the trash. While the rest of the waste paper burns down there is one piece hanging over the top edge that doesn't burn, even being in the midst of the flames on that side.
Revealing mistake: When the men are in ranks for roll call, it's snowing heavily. Given the pitch of the barracks' roofs, there shouldn't be any snow sticking. Therefore, if looked at closely, it can be seen that the "snow" on the roofs is painted in place.
Revealing mistake: When Hogan, Newkirk, and Carter are at the Blue Baron's secret airfield, Hogan opens the barrel and stuffs in a rag and lights it so it will be a flare for the Allied bombers. The flight line and the planes on it are an obvious cutout. The fire couldn't have spread to the surrounding ground like it was shown. Also, when the bombs were going off on the airfield, you can see that the explosions are very small charges behind the cut outs.
Revealing mistake: During the attack with crossbow, look closely at the arrow in the door. You hear the sound of the arrow hitting the door, then see the (now skewered) hat shaking on the arrow. If viewed closely, you see a black thread pulling on the arrow. Also, the arrow is almost straight before the break, then it is down at an angle when Shultz is called in.