X-Men: First Class is top of the list for errors over at Movie Mistakes, and while some of these are a little petty (the continuity errors for example, when this movie is believed to only be very loosely linked to Bryan Singer's X-Men and X-2 rather than The Last Stand and X-Men Origins: Wolverine) most are pretty bad mistakes! Personally, I only noticed a couple of these, none of which ruined the movie for me or took me out of the moment.
Visible crew/equipment: In the scene where Sebastian Shaw is reveling the Magneto helmet to Emma Frost in the submarine, you can see the microphone in the helmet's reflection through the entire scene.
Factual error: When the US & Soviet navies attack the mutants on the beach they fire a large volley of surface to surface missiles. This is supposed to be 1962, the Cuban Missile Crisis, and ship launched surface to surface missiles had only just been introduced and weren't very common. But what makes this a technical error is that in the barrage we see RGM-84 Harpoon anti-ship missiles, introduced in 1977, and RGM-109 Tomahawk missiles (could be anti-ship or land attack) developed in the 70s and first entering service in 1983.
Plot hole: *Spoiler* At the end of the film Xavier is shot, which leaves him paralysed, but in Wolverine and X-Men: The Last Stand we see a much older Professor X walking.
Continuity: The position of the pig farmer's hand moves after Erik stabs it to the table towards the end of the scene.
Factual error: In the beginning of the film, Shaw gives young Erik a coin. This coin is a 5 mark Nazi coin dated 1934, yet the coin was only produced from 1936-1939.
Other: After Prof. X has been shot and is in Moira's arms, he moves his own leg in the background of Erik's recruiting speech.
Other: The knife used in the Argentina pub scene never has any blood on it, despite being driven into one man's stomach and another man's hand-twice.
Continuity: In First Class, Professor X is made handicapped in 1962 at the end of the movie. In the previous X-men movie, he was walking when he visited the girl (Jean) in the mid 70s with Magneto.
Continuity: In a scene where Xavier is pointing a gun at Magneto the distance between the gun and Magneto's head changes between shots.
Continuity: In the original X-Men film, Xavier mentions that he met Magneto when he was 17. In this film, he doesn't meet him until well into his 20's, even after he becomes a professor.
Factual error: The establishing shot of Shaw's boat says they're in Miami. Yet in the scene, we see a very large suspension bridge in the background. That's the Sunshine Skyway Bridge in Tampa, not Miami. It also helps to know that that bridge was built in 1982, not 1962.
Factual error: Erik arrives in Argentina at a place called Villa Gesell, shown to be a town in middle of mountains. Villa Gesell is a beach town on the Atlantic Ocean coast, with no mountains.
Factual error: A Westland Bell 47G helicopter with the a registration of G-CHOP is seen to land at the Russian army camp/military headquarters when Charles, Magneto and the X-Men are approaching. The registration denotes it is a British aircraft, so unlikely to be in the middle of Russia, and this particular model was built in 1966 - four years after the Cuban missile crisis
Continuity: In this movie, Emma Frost is seen as an adult woman (roughly around the same age as Professor X and Magneto). But the character is also in X-Men Origins: Wolverine, set years later when Professor X and Magneto are much older, but she is much younger.
Factual error: In the scene where they first pull up to the mutant research facility, they are in a 1972/3 Cadillac when the movie is set in 1962.
Continuity: In the scene where Erik confronts Shaw on the boat, Emma's hairstyle changes from being down to being in a half updo right after Shaw chastises her for harming their own kind.
Factual error: When sitting in Xaviers mansion there are cushions on the sofas made from a Sanderson fabric, Dandelion Clocks, this fabric was designed in 2009 but the film is set in 1960.
Continuity: When Mystique is on the exercise table and Erik lifts the bar off her, her right leg changes from stretched out to bent from the different camera shots.
Continuity: Hank McCoy transforms into his beast form in X-Men First Class. However, in X-Men 2 when Mystique meets the guard in the bar, Hank McCoy, without fur, is speaking on a live talk show on a TV in the background.
Continuity: When Xavier freezes Levene in the hallway he has a jet of water against his lips. In the next shot the jet of water is against his nose even though he didn't move.
As for
THOR, Marvel Studios were clearly a lot more careful than they were back in 2010 with
Iron Man 2. Again, nothing too awful, but these are definitely some real blunders in terms of film making rather than the factual errors seen above. Again, this certainly didn't ruin yet another fantastic movie for me, but here's the considerably shorter list in full.
Continuity: At the end when Loki goes to lock the Bifrost on Jotunheim, he's carrying Odin's staff and wearing a helmet. He slides the staff into the machinery to open the Bifrost then freezes the electrical streams (with the staff in the middle of it) and his helmet is gone. Thor comes in to stop him and he's got the staff back from inside the ice and his helmet is back.
Other: On one of the SHIELD monitors, "perimeter" is spelled "perimiter".
Continuity: In the cafe near the beginning of the movie, Thor is told that Mjolnir has landed west of the cafe. When he walks outside to go to the hammer, if you look carefully, the shadows of the surrounding scenery show that Thor is actually walking East instead of West.
Continuity: When the Destroyer arrives amidst the Shield agents, a coffee cup sitting on the dash of one of the vehicles spills over. The next shot it can be seen lying on its side. The reverse angle shot then shows it upright again.
Continuity: After S.H.I.E.L.D "borrow" Jane's research and Darcy says that they took her iPod, her hair can be seen blowing in the wind in the shots facing her left and not blowing in the shots facing her right.
Revealing: Just before Thor returns to Asgard, he and Jane are talking before they kiss, and in this continuous shot they are virtually the same height. However, in the rest of the movie, Jane is significantly shorter than Thor whenever they are pictured together.
Continuity: In the scene at the crater when Thor breaks in and then is fighting the giant SHIELD guard, the fight ends up outside, and it is pouring rain. Thor and the guard are both soaking wet during the entire fight. However, when the camera cuts to shots of Hawkeye, who is watching the fight from an open platform above them, Hawkeye is completely dry. The scene shows him out in the open with no covering and there are several clear shots of Hawkeye's face, but there is not a single drop of water on him.
Continuity: When Thor and friends first arrive on Frost Giants realm, rocks tumble and create debris - which disappears between shots.