Revealing mistake: In one of Pickett's charge scene the bayonets are obviously rubber.
Factual error: In the scene where the king attempts to seize the five members from Parliament, Cromwell makes a dramatic refusal to leave and proposes various "Laws" to prevent his arrest. Cromwell was not one of the five members whom the King tried to arrest and no law can come into force until it had been signed by the reigning Monarch anyway.
Factual error: When Lovell's daughter is complaining that the Beatles have broken up, she slams the album Let It Be into her rack. The scene takes place on the day of the initial explosion aboard Apollo 13, April 13 1970 - immediately prior to the Lovell family attending the screening of a television broadcast from the spacecraft. Let It Be was not released as an album until May 9th, 1970. In April Ringo was still recording drum tracks, not even possible for an advance copy to get out.
Factual error: In the shot of the infield at the Saratoga racetrack several Canada geese are shown landing. However, the calls inserted on the soundtrack are the quacks of mallard ducks not the honks of Canada geese.
Factual error: In the opening shot of the film, a big oak door opens - carved in it is the date 1862 - 42 years after George III died.
Revealing mistake: Just after Li Mu Bai tells Shu Lien that they are very close to her headquarters and that she should check in, we are treated to two 'time pass' shots of forest. The second of these features some very obvious power or telephone lines in the lower right corner of the screen. (01:22:40)
Visible crew/equipment: In the scene near the beginning of the film, when the 2 brothers are fixing to leave to join the army. After the mother gives them the flag, the shot changes to the 2 brothers. You can see the boom mic and the camera in the reflection of their shiny brass buckles.
Continuity mistake: When Leonidas, and presumably all the other Spartans, use their spears to clear their shields of arrows after the arrow shower from Persian archers, the tips of the arrows are still visibly left on all their shields. In the next shot, when the Spartans regroup for the Persian cavalry charge, the arrow tips are gone. (Granted, this is a highly stylized movie based on a comic book, but that does not change the fact that this is a continuity error.)
Factual error: Another flag gaffe: The Canadian flag in the 1920s was either the red ensign or the Union Jack. The Maple Leaf only became the national flag in 1965.
Other mistake: About 3/4 of the way through the film a boat arrives at the left quay of the Seine. Looking west down the river with Notre Dame on the right of the scene you can see a tour bus cross the bridge.
Factual error: I normally wouldn't bother with this sort of nitpicking, but this film specifically claims to be historically researched - and it's full of historical blunders. For a start, the film is set as the Empire withdraws its last troops from Britain - which was in 407 AD. Now Artorius Castus was a real Roman officer who really did command Sarmatian foederati at Hadrian's Wall, but he died around 200 AD. Cerdic was a real Saxon warlord who did go raiding the Britons with his son Cynric, but he did this in the early 500s. Pelagius really was tried for heresy, but he was acquitted and died of old age; the trial was a decade after this setting, and in the fifth century you couldn't be executed for heresy anyway. Also in the fifth century the Pope had no authority over Imperial troops. I could go on and on but that will do for now.
Factual error: In the scene where there is a train passing, the cars are marked "Burlington Northern." There was NO Burlington Northern until 1970, 7 years AFTER the shooting.
Factual error: The third member of the Yankees with a prominent role in the film is Bob Cerv (roommate of Mickey & Roger). In the film, he is with the team from Opening Day. However, Cerv was actually acquired by the Yankees in May of that year.
Continuity mistake: It is 1940. Two pilots come out of a house - one of them has just lost his wife and family in the London Blitz, the other is an RAF Squadron Leader. The door they come out of has a modern electric bell push - a post 1965 version, white rectangular box with a round button.
Revealing mistake: In the scene after the battle of Agincort, where Henry and his retainers are walking meditatively among the heaps of the fallen, if you look carefully, you will see one of the fallen with his head raised watching the procession. He then realizes that he is on camera and puts his head back down. It's near the edge of the screen so may occasionally be cropped.