Plot hole: When Andy turns into a werewolf, he kills both Amy and Detective Benbou. Later in the morgue, Amy tells him because of this that she is forced to become his "rotting sidekick." If this is completely true, then Detective Benbou should also be following Andy around but he isn't seen after Andy manages to escape from the morgue.
Revealing mistake: On the ice the tank is firing - in slow motion we see empty shells are littering the area. The shells have crimped ends, revealing them to be blanks.
Revealing mistake: When the kids are burying Gus, his supposedly dead face flinches when they shovel dirt on him.
Revealing mistake: When the new Pope is announced, the New York Times headline is shown, and 'Copyright 1990 The New York Times' is visible. The event took place in 1979.
Continuity mistake: When Nick is sitting on the bed talking to Jessica, her position changes from lying on her side to lying on her back, as the camera angle changes.
Continuity mistake: When the police are moving in to arrest Dzhokhar Tsarnaev, the shot shows an FBI SWAT officer grabbing him. But in the next cut, the officer changes to a Boston Police Officer while changing back to a FBI Officer in the following shot.
Visible crew/equipment: When Dennis Weaver is in the cafe a shadow of a cameraman is cast across the table he is sitting at. The shot then changes to a wider angle to reveal that there isn't anyone near him who could have cast that shadow.
Factual error: The movie takes place during the 1990s, but throughout the movie cars are shown with Illinois license plates with "Illinois" written in cursive. These plates were not introduced until 2001. (00:24:45)
Continuity mistake: Daniels' face gets splattered with blood, in a following shot there's slightly less blood, then when she uses the radio to call back the others, her face on the screen shows no blood at all. In the other shots after it's there again.
Factual error: A map in the office of Policeman Pierce Brosnan showing the "Hillside Lake" is Lake Constance (Bodensee) in the south of Germany. (01:11:00)
Revealing mistake: Before Paxton is hit with the 3 prong instrument, you can see the bloody holes already on his shirt. (01:01:20)
Continuity mistake: When surrounded by police and a garbage truck, Frank drives his car from the overpass onto the passing transport trailer below, then lands behind a hatchback and in front of two cars - a white compact with a sunroof and a grey hatchback. In one specific shot from atop the trailer, as Frank rolls his window down (before he requests the gun) the only vehicle behind Frank's car is the white compact, which is at the trailer's rear. Note things such as the trailer's safety bars, and the view through the compact's windshield for starters. That grey hatchback is back when the ramp is lowered, for the ensuing crashes. (00:08:20)
Continuity mistake: When Eliot Ness is at Jim Malone's house for the first time, Malone's collar is opened, then buttoned, then open again.
Revealing mistake: When Sonny is punching Carlo under the spraying fire hydrant, he misses an audible punch by at least six inches. (01:43:30)
Continuity mistake: Towards the end, Denzel drives his car into 2 cars trying to get Ethan off the hood. After that scene ends you see Denzel driving the same car and the front and rear of the car look nothing like they did when he was crashing into the cars.
Revealing mistake: If you look at the missing part of the bridge, and look at the shadow underneath, the shadow is of a full bridge. (01:02:35)
Continuity mistake: When Magneto lands the Golden Gate Bridge on the island, as it hits land it is still very light. When the Brotherhood start to walk toward the island, it cuts to a wide shot of them still walking on the bridge, and it's suddenly dark.
Factual error: After the intruders flood the panic room with propane, Jody Foster's character gets a lighter and ignites the propane causing it to burn along the ceiling. This would be impossible as propane is heavier than air and would sink to the floor rather than rise up to the ceiling. Lighting a flame in that room should have caused anyone in the room and on the floor to be engulfed in flames almost instantly.
Visible crew/equipment: At Hoover Dam, after the salute, when Defense Secretary Keller speaks with Lennox and Epps, the reflection of the white reflector screen is visible on Keller's glasses. What's more, the boom mic's reflection is actually visible within the reflector screen's reflection. Two for the price of one. (01:35:30)
Continuity mistake: When Blair asks Mitch "why aren't you answering me?" he says he got a weird message from Laura Barns. Blair replies "that's not funny" and Mitch replies "I'm serious." Then Blair gets a message from Laura, and when she switches back to Mitch's conversation, the last two entries, "that's not funny" and "I'm serious" have disappeared. (00:10:50 - 00:12:30)