Factual error: During the bar scene in Argentina, Magneto uses a dagger he took from one of the former SS Soldiers. It appears to be a Reichsarbeitsdienst dagger with the inscription "Blut und Ehre." This is incorrect as the inscription should read "Arbeit Adelt." "Blut und Ehre" was inscribed on Hitler youth knives as that was their motto.
Continuity mistake: When the young mutants are showing each other what they can do, they all have a glass of cola, all four sitting on a corner of the table. But when Banshee wants to show what he can do, the glasses are instantly lined up. (00:51:00)
Continuity mistake: When Banshee is diving into the water, his "wings" are still attached. The shot angle changes, and his wings have disappeared before hitting the water. (01:39:20)
Continuity mistake: Towards the end, when Moira is pushing Xavier's wheelchair in front of the X-Mansion, when they stop, Xavier's wheel's position change between shots without them moving.
Other mistake: Near the end of the film, Magneto finally kills Shaw by pushing a coin through his brain. The blood on the coin is already dry when it hits the ground, even though only seconds have passed, and since we're shown blood leaking from the entry wound later, we know that it wasn't dry to begin with.
Factual error: Miniskirts weren't in fashion until at least 1965-66, and the high rise hemlines worn by many female characters weren't around until '68 or '69.
Continuity mistake: When Magneto is in Argentina, the two guys sitting at the bar change the distance between each other, between shots.
Continuity mistake: In the original X-Men movie, Professor X wonders why he can't read Magneto's thoughts, only to learn that Magneto has his special helmet. First Class contradicts this by establishing that Xavier knew about the helmet in 1962.
Factual error: The scene at the beginning is set at a German concentration camp in occupied Poland in 1944 (as annotated). When Erik enters Shaw's office, the song "La Vie en Rose" by Edith Piaf is playing. The song wasn't written until 1945 and wasn't recorded until 1947.
Continuity mistake: During the bar scene when the bartender is pouring beer for Eric, more than half of the glass is filled with foam (though it's in the background you can see it). But straightaway into the next shot when the bartender passes the beer to Eric, there is only a little amount of foam. (00:22:55)
Factual error: When the US government deliberates about blocking access to Cuba, they request the 7th fleet to be dispatched for the blockade. The 7th fleet is on the Pacific Ocean, not on the Atlantic. (01:47:00 - 01:48:00)
Continuity mistake: Erik meets two Germans at the bar in Argentina, a pig farmer and a tailor. The amount of beer in the farmer's glass increases after Erik walks towards him. (00:23:20)
Factual error: When Erik pulls the bullet out of Xavier's back, the bullet should be covered in blood, but it is completely dry.
Continuity mistake: Before Shaw takes the grenade from Hendry, the latter one has his finger in the pin, and has it half pulled out by then. Look closely at Hendry's hand: he is still holding the pin, while Shaw takes the rest of the grenade, but in the next shot, Shaw pulls it out again. (00:28:10)
Factual error: The Cuban Missile Crisis was in 1962. Rossiya Hotel (shown in the background of the Red Square overview) was built 1964-1967. (01:10:05)
Continuity mistake: When Erik is about to lift the submarine out of the ocean, most of the hand he is using isn't that clean. However, after lifting the submarine out of the ocean part way and the shot cuts back to Eric, most of his hand is clean.
Other mistake: In the version I watched, the subtitles that cover Sebastian Shaw's conversation with the Russian leader, had typos - the word 'missile' was spelled 'missle' on two, possibly three occasions and the word 'placed' was spelled 'places'.
Factual error: The CIA is operating within the United States, given that they're not allowed to do so. Everything the CIA did in the film really should have been done by the FBI.
Continuity mistake: The Nazi doctor shoves a coin towards the edge of his desk, telling young Erik to move it or he'd shoot his mother. In a shot from behind the desk, the coin is much closer to the edge than in other shots. (00:07:15)
Revealing mistake: In the submarine, when Emma goes to get ice for Shaw, Azazel's tail is missing when he helps pull the submarine's ladder down.
Suggested correction: Xavier has frozen Shaw in place with telepathy. Thus, the reason why the blood appears dry on the coin, is because it is still Shaw's essence, and is still technically frozen in place.
Telepathy doesn't physically freeze a body. He is forcing his mind to stand still.
lionhead