Factual error: The Königsstraße in Stuttgart is located in the city's main shopping area, not its cultural center as the film would suggest. (00:37:20)
Continuity mistake: When Maria Hill is being attended to after she gets hurt, her earpiece is on the left side of her face. In the next shot she is talking to Nick Fury and her earpiece is on the right.
Continuity mistake: 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. (02:08:30)
Continuity mistake: When Agent Coulson is dying, Fury grabs Coulson's chin with his hand. The hand disappears in the angles shot from behind, only to reappear in the front ones. (01:28:05)
Continuity mistake: While Loki lies on the floor and talks about the Tesseract, bushes appear/disappear by his left side between shots. (00:43:00)
Continuity mistake: For a brief moment during the battle at the end, the scar on Tony Stark's left cheek vanishes after saying "I will, roger that" to Hawkeye. It reappears shortly afterwards. (01:54:15 - 01:54:55)
Continuity mistake: 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. (00:32:55)
Continuity mistake: 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. (00:34:15)
Audio problem: In the scene where Black Widow is hanging off the back of the flying Chitauri chariot, one of the Chitauri fires his gun, but there is no sound effect to go along with the blast as there is with the other blasts. (01:51:50)
Continuity mistake: 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. (00:24:30)
Continuity mistake: 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. (01:40:35)
Continuity mistake: After Hulk smashes Loki against the floor, the amount of rubble around Loki changes between shots. (01:55:25)
Continuity mistake: Sunlight is alternately on the top of Captain America's head or not when he tells the two policemen to get the civilians off the streets. (01:44:50)
Revealing mistake: In the scene after the Chitauri army enters the atmosphere, they start shooting people in the ground and in the next shot if you see underneath the bridge there is a restaurant with people running around to avoid getting hurt. If you see there are two glasses of wine and some food plates sitting in a table firmly which does not even move despite the blast wave that was created from all the shooting in the ground near it. (01:43:15)
Continuity mistake: 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). (00:14:15)
Continuity mistake: 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. (00:21:15 - 00:21:55)
Continuity mistake: When Rogers, Banner and Stark are discussing about Stark Tower, the tools on the table move around.
Revealing mistake: During the climactic battle towards the end of the film, when Hawkeye fires his arrow and rappels through a window, the camera pulls in close to him. Watch as he begins to roll over: He rolls over a piece of glass, which smushes up like jello under his elbow. It's obviously a piece of stage-glass. (01:57:30)
Continuity mistake: 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. (00:06:15)
Continuity mistake: When Loki says "You don't have the Tesseract yet", The Other moves to him with his right hand raised. The shot cuts and it is now his left arm. (00:30:40)
Answer: People have been smuggled in and out of countries for decades, grease the right palms and talk to certain people, if you don't get in under the radar, phony papers could.