When the helicarrier starts to go down, Nick Fury tells Iron Man, "Stark, we're losing altitude," and display inside Iron Man's faceplate is counting down from about 15,000 feet. A few minutes later when Fury glances at a display on the bridge, it is counting down from 18,000 feet.
After Captain America stops Iron Man and Thor from fighting, Thor knocks Iron Man behind him a good distance before hitting Cap's shield. But when the dust settles not only does Iron Man wake up pretty much next to Cap, he is also in front of Thor somehow.
During the final battle, Iron Man explodes a "Leviathan" - one of the big Chitauri monsters - from the inside, labeling his attack 'Jonah-style'. He falls and hits a cab, which stops him. The camera angle then changes, and the cab is nowhere to be seen.
When Capt. America is in the gym punching the second bag, the bag has no tape around the middle. When he and Fury begin talking, a close up of the bag has duct tape around the center. Next it switches back to clean again.
In the closing sequence in the shwarma restaurant, Thor is sitting among the heroes, although he left with Loki earlier. If this scene were to have occurred before his departure, a pouting Loki should have been evident, as there is no reasonable way Thor would have left Loki unattended on Midgard.
The number of soldiers accompanying Hawkeye during his attack on the Helicarrier is inconsistent. We see 7 soldiers with Hawkeye when they enter through the grate on the deck, however we see a total of 8 during the subsequent scenes. 2 are killed by Nick Fury and 1 by Maria Hill in the initial shooting on the bridge. We then see another 3 at the damaged engine fighting Captain America (he knocks one out and throws another off the ship - the final one is knocked out by Iron Man). Another soldier is shot by Fury in a subsequent bridge scene and finally the 8th is subdued by Coulson in the detention area.
In the very beginning of the movie, when Black Widow is being interrogated, she has bracelets on her right hand. When she is fighting the guys her bracelets keep moving from the right to the left and finally back to the right hand.
After Loki shoots down the aircraft containing Hawkeye, the Black Widow, and Captain America, the three Avengers are standing near the wreckage, looking up at the invasion of the Chitauri, which is just beginning. A group of extras is seen fleeing the area in the background. Several minutes later, the same group of extras is seen running past the Avengers - again.
When Nick Fury is talking to Steve Rogers in the gym we see Steve from in front removing the bandage from his right hand, when the scene cuts to Steve from behind he is removing the bandage from his left hand, when it cuts back to the front view he is removing the right hand bandage again.
Hawkeye shoots an explosive arrow at the helicarrier and damages it. During the explosion, the helicarrier remains visible as if it didn't have its cloak on but another scene shows the helicarrier decloaking due to the damage.
The plane with Captain Rogers and Agent Phil Coulson lands on the carrier you see a crew member in an orange shirt directing the plane on where to land, he is close to the plane, when the shot changes to an overhead shot he is not near the plane.
Agent Phil comes to the Stark Tower to meet Tony. Pepper hands him her glass of champagne. During Pepper's conversation with Agent Phil, he holds the glass by the bowl, but in one shot he is holding it by the stem.
Right after the second engine goes down on the shield Helicarrier, the altitude reading on Iron Man's HUD shows just over 15,000 feet for the altitude. A short time later, even though the helicarrier has been falling since the engine went down, the altitude on the helicarrier's bridge shows the helicarrier falling through 18,000 feet.
When Tony goes after the nuke, there is a huge cut visible above his right eyebrow (or viewer's left). Later on after his face mask is removed, his right eyebrow is completely visible in the shot, even with the helmet in the way, and the cut is nowhere in sight.
When the Helicarrier is attacked and Bruce Banner and Black Widow are thrown out of the lab, a wrist watch with a black band can be seen on Banner's wrist. By the time he growls, "Your Life!" at Black widow, as he starts to change into the Hulk, the watch has disappeared. And no watch is visible on the metal flooring when he crawls/scrabbles away from her.
During the big battle against the Chitauri, Captain America is zapped with a blaster bolt. When Thor helps him to his feet we can see a significant amount of damage done to his suit, just below the star on the right hand side. But later on after Iron Man destroys the Chitauri ship with the nuke, the damage is completely gone.
After the Chitauri have arrived, Loki stands on the Stark Tower balcony and looks on New York. In this shot, Loki is standing facing the city directly, but by the next shot, he's suddenly standing 90° in the other direction with his head turned to the right, in order to be looking the same way as in the previous shot.
When Captain America, Black Widow and Hawkeye are fighting their way through the Chitauri in the S.H.I.E.L.D. jet, one shot shows the Chitauri blasting at the jet causing part of the front of one side to get blasted and a burn mark is left on the jet. A few seconds later, Loki blasts one of the engines and the burn mark on the front of the jet has vanished.
Capt. America has just destroyed the first punching bag and walks away to pick up a new one. There are now 5 bags left. Note the chains belonging to the third one from the left. The way they lie on the floor differs in from shot to shot.
When Hawkeye is breaking onto the Helicarrier, he and some snipers break down a duct cover and enter. When the cover lands on the floor, it is resting away from some pipes with some slats missing. As soon as Hawkeye enters the duct, the cover is now resting against the pipes, and the slats have reappeared.
When Steve and Coulson land on the Helicarrier, you can see two wings on the edge of the Quinjet they were in and they are both closed up. Next shot, as Romanoff approaches the Quinjet and Steve and Coulson exit, we can see one of the wings is completely open.
In the scene where Loki escapes with Hawkeye and Agent Hill is chasing them, she does a 180° spin and ends up face to face with Loki's driver. She shoots through the glass and you can see the bullet hole, but during the rest of the scene, the hole is gone, or moved to the passenger side.
During the battle of New York, Thor has just landed next to an upturned silver car. The rubble around the car changes/moves. The most noticeable is one wedged next to the front right wheel. The piece becomes much bigger in the next shot.
Coulson walks into Stark's office and hands Pepper the file on the Avengers, which she promptly passes on to Stark. In the front shot, she is holding the champagne glass down by her waist. Cut to the shot from the back and you can see the glass just above her right shoulder.
When Tony arrives at Stark Tower, he and Pepper share a bottle of champagne. In the shot where he says "Next building is going to say Potts on the tower", Tony's champagne glass is in his hand and there's no sign of another glass several inches either side. In the next shot, Pepper's glass is suddenly 2 inches away.
After the big battle, Iron Man lies on the street when Capt. America, all dirty and messy, says "We won." Iron Man sighs in relief and rests his head on the pavement. A frame later, from a wide angle, his head is raised, plus Capt. America's face is clean and his hair is brushed.
After the Tesseract opens up the portal that Loki enters from, 4 SHIELD guards are seen slowly advancing on his position. On the left side of the device, two of them are moving. The one further behind walks over an area of the floor that is illuminated by some orange light. The shot cuts to his feet, and suddenly the floor is dark.
In the beginning of the scene "Mountaintop Battle" while Loki and Thor argue, Iron Man flies into Thor, tossing him to the ground below. Thor's hair is messed up and dirty. The shot changes, and when it goes back to him, he is standing and his hair is clean and neatly combed.
When Natasha is tied on the chair and the phone falls on the floor, it disappears, then reappears but turned off, and finally we see it with a shining bright green light (as it was supposedly left by her, when she left the call on hold).
When the Helicarrier is about to take off, Banner and Rogers are still at the edge of the landing strip, identified by the yellow SHIELD logo and the jet that Banner is checking out. But the shot hangs on Romanoff for a second, and when it cuts, Banner and Rogers are instantly at the very edge of the ship, a good 50 feet away from where they were a second ago.
When Thor smashes the hammer against Captain America's shield, they are pushed at least ten feet away from each other. Yet when Iron Man gets up and walks over to Captain America, the two are suddenly much closer together.
When the plane lands on the aircraft carrier, it is about to land on a yellow mark on the ground. The angle cuts and it's now landing in front of it. Then from the aerial angle it lands on the middle of both lanes, but a frame later it's on the right lane. Finally, the landing signal officer swaps from standing in front of the plane waving his arms, to several meters behind standing still.
When Stark is about to fire up the arc reactor underneath Stark Tower, you can see that he turns for his approach. But when he is flying in with the nuke, Stark Tower is in a straight line with the street he flew in on - the same street as when they lit the arc reactor.
When Captain America and Coulson land on the Helicarrier in the jet, there is a man with an orange coat standing 2 to 3 meters away from the helicopter. In the next shot, he is at least 6 to 7 meters away from the jet.
There is a deleted scene of Steve Rogers looking through the files of his former comrades. When he first reads the sheet for Peggy Carter it has her address printed in a modern typeface on a label stuck to the page. The next time we see it, the details are the original typeface on the original paper.
Right after Loki's mind control spell finishes taking hold over Hawkeye, Loki begins pulling back and Hawkeye is facing him but turned at an angle. The camera cuts while Loki is still moving his spear away and suddenly Hawkeye has a little more distance between him and Loki, and he is turned to be almost fully facing him.
As Nick Fury and Selvig are talking about the Tesseract, an overview shot is shown where Fury says "I assumed you pulled the plug" and Selvig says "She's an energy source." This shot shows Fury and Selvig in the far background and we can see they are standing even with each other, but in a sudden close-up of the two, Selvig is suddenly standing in front of Fury.
Selvig is carefully moving a cylinder of iridium from a scale to its final location with a metal tongs. The way he holds the tongs changes, when it is highly unlikely that Selvig would change his grip while moving such a delicate substance. Most noticeable are his index and middle fingers.
As Nick Fury is telling Agent Hill that he will act as if the world intends to spin on, and to clear out the tech below, the first shot from behind her shows she has her head leaning slightly to the right. It cuts to a frontal view of her and her head is leaning slightly to the left.
After Hawkeye fires an arrow at the Helicarrier and part of it explodes, Bruce and Romanoff are knocked out of the room and land on a lower level. As they land, they are shown to be right next to each other, but when they are shown next, the distance between the two has increased by at least two feet.
Once Iron Man finishes with his project underwater, he surfaces and begins flying towards the city. The view from behind shows a very long and noticeable vapor trail coming from his jet boots that stretches far back. But when the shot cuts to being in front of Iron Man and going with him, the vapor trail is much shorter, dissipating quickly, and hardly noticeable.
When Thor says "I have unfinished business with Loki", you can see Hawkeye in the background removing the spent heads of his arrows, four of them, two a little lower then the rest. The shot cuts, and he is holding all four at the same height.
In the fight scene between Thor and Iron Man, after Captain America tells Thor to put the hammer down, Thor slaps Iron Man, who is to Thor's right side, back several feet away from them and then jumps even further away. After Thor hits the Captain's shield, as they are all getting up, Iron Man is right next to Captain America and Thor, now to Thor's left side, (when he should be about fifty feet away and still to Thor's right side). Even if Iron Man made it back to Captain America before the shock wave, he should still have been visible before the shock wave for his position on the ground to be possible.
In the scene where Agent Coulson enters Stark Tower near the beginning, as he enters, Pepper looks up at him. In the next shot, she is looking at Tony, and then in the next shot, she's looking at Coulson again.
Just after Dr. Banner asks Nick Fury how many spectrometers the Helicarrier has access to, he takes off his jacket, rolls it up, and puts it under his arm. In the next shot, without Banner moving, the jacket is suddenly draped over his arm.
When Loki and mind-controlled Hawkeye are leaving the S.H.I.E.L.D. base with the Tesseract, Agent Hill asks Hawkeye of Loki: "Who's that?" and Hawkeye replies: "He didn't tell me." Yet only minutes earlier Loki announced to a room full of people, including Hawkeye: "I am Loki of Asgard."
The reception scene said to take place in Stuttgart, Germany, was clearly filmed in the U.S. (Cleveland, in fact) There are no such skyscraper buildings in Stuttgart as seen in the background. All S-Class Mercedeses shown are U.S.-spec-models, easily recognizable by the yellow front side marker lights. Furthermore, Königstrasse is mainly a shopping street, and Königstrasse 22, in particular, is a shopping arcade containing, among a dozen shops, two cinemas. There is no building in the vicinity higher than half a dozen floors, and Königstrasse 22 opens on the street, not on a square. Furthermore, Stuttgart has no elevated trains, which can be seen in the background of the square scene.
In the very beginning of the movie, when Black Widow is being interrogated, the exterior shots shows a billboard with supposed Russian writing. However, the actual writing makes no sense and is just a collection of random Cyrillic letters. Additionally, the locomotives of the train seen passing by are all new American mainline freight locomotives, and would never be used in Russia or Eastern Europe in general.
When Thor takes Loki from the jet being flown by Black Widow, Tony Stark leaps out after them, already in full Iron Man armor. It takes several seconds for Captain America to put on his parachute and dive after him. By that time, the jet would have been several miles away. Tony had no problem catching up to Thor because of his rockets. Captain America, however, has no rockets, so there's no way he would have landed anywhere near Thor and Loki.
The German police cars shown in the Stuttgart-scene have yellow light bars. In reality all German emergency vehicles have blue flashing lights. Yellow flashing lights are generally used as a warning signal, i.e. for roadside assistance, construction machinery or garbage trucks.
When the computer locates the Tesseract's location while the Avengers are arguing with Nick Fury, the computer displays the location with Latitude & Longitude coordinates that doesn't conform to the format it's displayed in. "LAT:45°66.12 'N /LON:76°87.32'W" is shown, the format is degrees & minutes. The minutes must be between 1 to 59, here we can see 66.12 and 87.32 are greater than 59 and not a valid way to display minutes in this format. If input as a correct degree/minute display of 45.6612 N 76.8732 W the location is actually on a country road just northwest of Ottawa, Ontario, Canada and not New York City.
S.H.I.E.L.D. Quinjets flying at night are shown with red navigation lights on each wingtip. There should be a green light on the right (starboard) wing, and a red one on the left (port) wing. These are known as Right-of-Way lights, and follow the same rules that were established for watercraft in the mid-1800s.
Many of the S.H.I.E.L.D. agents aim their M4 carbines by sticking the buttstock of their carbine under their armpit. No trained law enforcement or military personnel would ever do this in combat. They would actually shoulder their rifles, which provides better stability and makes the weapon's optical sights properly line up with their eyes.
Several times in the movie, inhabitants of Asgard are called "Asgardians." While this could be excused as ignorance, Loki should surely know the correct term, "Aesir," and Thor should surely corrected its use when he heard it.
After carrying the nuke through the portal into space, Iron Man falls back through said portal. You cannot fall in space, since there is no gravity - he would simply keep moving in the direction he was already going, towards the alien spacecraft.
When Tony Stark confronts Loki at the Stark Towers and tries to stall him by offering him something to drink, he brings the glass with him and sips from it. The scene briefly (maybe 2 to 4 seconds) goes to Loki then back to Tony Stark. Tony Stark is no longer holding that glass of alcohol.
In the end-credits scene, the Shawarma restaurant is indicated by signs, t-shirts, and a chalkboard with shawarma, kabob and vegetarian specials listed. However, the back-lit menu at the top clearly shows steak, sandwiches, soups, Thai chicken salad (among others) and onion rings, and no indication of shawarma, gyros or other middle eastern/Mediterranean fare.
Where the little girl in Kolkata searches for Dr. Banner, the Bangla signboards have typographical errors: 'Chemist' was written in Bangla like 'ka-me-sit', 'Watch Service' appeared as 'ghardir da-o-kan. Even 'Centre' was partially seen to be written as 'ka-ne...'.
This most possibly occurred due to transliteration from english to Bangla unicode.
During the fight between Natasha Romanoff and Georgi Luchkov (Jerzy Skolimowski) Luchkov's hair changes length and whiteness between shots revealing an obvious stunt double in place of Skolimowski during the more physically-demanding shots.
The goof item below may give away important plot points.
When Iron Man takes the nuke through the wormhole, we see the wormhole is directly above Stark Tower. As he falls back through, he should have still been directly above the Tower. Instead, he seems to be falling closer to the rest of the Avengers, who are located several city blocks away (as evidenced by the Hulk being able to jump almost straight up to catch him, and the others running over within seconds).