Character mistake: At the beginning of the movie, the German sub gets surprised and severely damaged by a destroyer. The sonar man first notices the enemy destroyer approaching, but only a short time before the destroyer is already literally on top of the sub. German sonar at the time had the capacity to detect ships up to more than 7 miles away, so the sonar man really had to be asleep at his sonar station not to notice the destroyer approaching. (00:03:40)
Character mistake: The scene in the outdoor Parisian cafe is incredibly daft. First, the cafe owners call James Coburn's bizarrely-accented Australian to the telephone to keep him out of the way as their accomplices assassinate three uniformed German officers seated in the cafe in a drive by shooting. They then toast the killings with cognac, and that is the mistake - not the shootings, not the luring away of Coburn - the mistake is that the cafe proprietors celebrate the assassination of the German officers in broad daylight, in the open, without even stopping to think that such an action would have them shot, because all of this is done in the direct view of passers-by in broad daylight. Do they think those three German officers were the only ones in Paris? How did they know Coburn wasn't an undercover Gestapo agent or a French collaborator? Don't they stop to consider that in an occupied city machine gun fire is going to draw some attention from the authorities, who might just wonder what a couple of bullet riddled corpses are doing lying about the place?
Character mistake: On the way approaching town the camera pans to a woman's hanged body with a sign written in German around her neck. One of the crew asked Wardaddy what it said, to which he answered something like "It reads 'I am a coward who refused to fight for the German people'." That sign actually translates to "I wanted my children not to go fight" or Anglicized for better effect, "I refused to let my children to go to war." Interestingly, once into town, there appears the corpse of a hanged man with a sign written in German that does translate to what Wardaddy said of the first sign.
Character mistake: In the courtyard of the castle there is an anti-aircraft gun. You could probably not find a worse place for a gun like that even if you tried (except maybe if you put it inside, in a windowless room). In the position it is placed it can only fire at targets directly above the castle. What you want to do is fire at targets before they reach the castle. It would be better if they placed it on the roof, or even near the village below.
Character mistake: In a conference with Crockett and Bowie, Travis states that Fannin in Goliad is preparing to relieve the Alamo and will be ready to "march south by the end of the week." Goliad is 90 miles south of San Antonio. To relieve the Alamo, Fannin would need to march north.
Character mistake: When the Marines are navigating through the Paris Island obstacle course, Hartman is shouting "It should take you no less than 10 seconds to negotiate this obstacle!" In other words, the LONGER it takes someone to get across, the better? (00:13:27)
Character mistake: When Cronauer and Garlick get stuck in traffic with the Army trucks, Garlick asks the assembled troops to guess who is in the Jeep with him. One of the troops shouts "Mork". Robin Williams played Mork in Mork & Mindy, but not until 1978, well after the setting of this film.
Character mistake: When Doug Masters approaches his aircraft at the airfield before racing 'The Snake', Col Sinclair has a right hand access panel open on Doug's Cessna 150 upper engine cowling and is allegedly working on the fuel system saying "As lean as you were runnin', if it went into a stall, you woulda lost your engine, and would never been able to pull it out." The carburetor, gascolator, throttle linkage and carburetor control lines are on the bottom of the engine (Continental O-200). The panel he closes after sticking bubble gum on accesses the battery, the right hand magneto and the oil dipstick. Not only did Col Sinclair not do what he said he said he did without a sign-off in the aircraft's logbook, it would be totally unnecessary, as aviation updraft carburetors use a cockpit or engine controlled fuel mixture control that would have simply been left in 'full rich' position after engine start for the altitudes the aircraft would have been flying. And stalling is an aerodynamic condition of angle of attack being exceeded or insufficient airflow over flight surfaces, not fuel starvation, which is the condition being addressed. (00:11:30 - 00:12:30)
Character mistake: When Barry Lyndon is talking to his mother privately, while standing on the bridge overlooking the water, Barry's mother refers to Barry's son Brian as being "at the mercy of his stepbrother", meaning Lord Bullingdon. They have the same mother. Lord Bullingdon and Brian would be half brothers, not step brothers.
Character mistake: The closing shot of a newspaper article shows the word "rumor", film is set in England where it's spelled "rumour".
Character mistake: In the scene where Crapgame is sitting in the back of the truck at the end, when the men are loading Kelly's squad's take after splitting with the Germans and Oddball, Crapgame asks Fisher to verify his calculations. There are 125 boxes of gold left valued at $8,400 per box. Fisher says that they are worth $10.5 million, and each of the twelve men in the squad will get $875,000. The actual amount (125 x 8400) is $1.05 million, making a per man take of $87,500. He's off by a factor of 10 one way or another.
Character mistake: Before the final attack in the village, we can see a wall with an advertising for Byrrh, an aperitif drink made from a blend of wines. The ad reads: "Byrrh, l'ami de l'estomach, " which basically means: "Byrrh, stomach's friend." In French, the correct spelling is "estomac." not "estomach." This is quite a big mistake since the ad and the building are three or four stories high.