Continuity mistake: When John Mills is looking through the periscope whilst searching for the German battleship the side view shows him moving the periscope from right to left, but when it suddenly cuts to a shot of what he is actually seeing through it the periscope is strangely moving from left to right.
Continuity mistake: During the opening of "This Is the Army" [the stage musical], there is a large choir of men singing the opening number, "Some Dough For The Army Relief": from about the second row back, the men's mouths are moving appropriately for the lyrics they're singing, but much of the front row is singing with these obnoxious cheesy grins, not even bothering with more than the most feeble attempt at proper mouth movement. [This is painfully evident during the line "let him do what we had to do."]. (00:48:50)
Revealing mistake: In this scene we see Cheetah jumping down from a tree to the ground. In the next shot we see Cheetah and a circle of light moves, which indicates they were using a mirror or even a light for extra lighting to brighten up the shot. This happens very briefly and is very noticeable.
Continuity mistake: In the scene where the tank crew meet up with the weary band of soldiers, Fred Clarkson (Lloyd Bridges) has a very distinctive graze on the right side of his forehead. It seems to disappear then appear then disappear during the film. When Clarkson lies injured there is no sign of the graze - there should at least be a small mark of the graze but there is nothing.
Factual error: When the troopships join up with the naval units, a Nevada or Pennyslvania class battleship with tripod masts is shown.however, in July 1942, Oklahoma and Arizona were sunk, and Nevada and Pennyslvania were undergoing repairs stateside.
Revealing mistake: When the mice are feeding the cat, the cat sits up and a mouse passes through his head.
Factual error: In the scenes set during 1918, Clive is shown wearing a typical late 1930s/WW2 military production British steel helmet with its distinctive canvas covered sprung chinstrap.
Continuity mistake: When Jerry launches his egg carton, there are initially three light bulbs in the back, but when he releases the bulbs, there are now four.