Gamble owns a red Prius. At one point, the right rear door is replaced by a gray door (due to events happening in the movie). Later, when the car is on a train, the door reverts to red. However, two scenes later, the car door is gray again.
As Terry is sliding down the board room table on his back, one of his guns falls out of his hand near the end. When he is on the ground, he has a gun in both hands.
After the explosion at the lawyers office in Jersey, Alan's wooden gun is on the ground. In the next scene, the gun is in its holster.
During the "Good Cop, Bad Cop" scene, Allen takes a painting off the wall and throws it down. Then it's on the wall again.
As the Prius is driving across the George Washington Bridge, the missing rear door is still covered with polythene sheeting. When they park at the Investment House in New Jersey, the plastic sheeting is replaced by a white door.
When Hoitz and Gamble are shocked with the stun guns they both pass out. A stun gun doesn't render a person unconscious. It has quite the opposite effect.
The second generation Prius (which Allen drives) does not have a button to open its lift-gate from the inside.
At one point Allen Gamble states that this is the second time he has ever fired his weapon, but earlier on when they're at the bar drinking there are multiple still shots of him discharging a firearm in the bar. However, at the time of the bar scene, he still had the wooden gun so he must have been shooting Terry's gun, thus still being able to correctly say he'd only shot his own gun twice.
When Sheila was telling Terry about Allen's FaceBack app, she said it can take a person's face and tell you what the back of their head looks like. However, in the closing monologue of the film, the narrator describes how Allen's FaceBack app helped police identify someone's face by using an image of the back of their head. This seems to be backwards from the way Sheila described it, but if they used Allen's app to generate an image of the back of Roger Wesley's head, they could compare that image to the image of the back of his head on the security footage, thus providing a match.
When Allen and Terry decide to start fresh while walking through the city without shoes, several bystanders can be seen taking pictures and videos of Mark Wahlberg and Will Farrell filming the scene.
When Allen turns around the white Ford van (Grand Theft Auto move), the van's reverse lights are on throughout the spin/collision.
In the close up of the red truck that Mark Wahlberg had to swerve and avoid a head on collision with, you can clearly see the road behind it was actually blocked off by cars that were queued across an intersection but weren't moving, and two police officers with high viz on, hands in the pockets, standing alongside several witches hats looking directly at the action and not moving a muscle.
Before the characters exit the garage in the chase scene, they race up to a stop and you hear a loud engine revving noise. The electric motor in a Pruis wouldn't make that sound at such a low speed.
After the explosion at the Accounting office, Will Ferrells wooden gun is in and out of his holster while he rolls around on the ground.
When Allen is having his flashbacks of how he becomes a pimp, the stack of $20 bills is of the current $20 bill. During that time period, it should have been the Series 1995 $20 bill.
When Allen's wife crosses the street dressed as her mother to come talk to him, Allen's dark ear piece is visible during their conversation.
A radio call goes out for a "211 in progress." 211 is the Los Angeles Police Department's code for an armed robbery, which is derived from the California Penal Code. The NYPD code for an armed robbery is a "10-30".
After Hoytz and Gamble are out for a night of heavy drinking, the film then dissolves to a shot of the Sun rising over a city skyline. Although the story is set in New York City, the skyline in the shot is actually the city of Boston.
In the closing credits, the globe is rotating in the incorrect direction. The Earth rotates counterclockwise, not clockwise.
At one point, the State Capitol building in Albany can be seen in the background, even though the scene takes place in New York City.
When Gamble and Hoitz get a call about a possible jumper at Beaman's office the location given is 3 World Financial Center 23rd Floor. The building shown is not World Financial Center.
When Ershon's lawyer goes to the police station, he gives them back their guns and their shoes, but not their car, and Allen Gamble doesn't even ask for it. It is simply found later.
When Terry visits the art gallery, he is told not to set his drink on the installation coffee table. When he looks closer to read the description card, the artist is listed as M.L. Pollard. But then Francine tells him that it is an original Habberfield Jammeson piece.
When the Captain relieves Alan of his sidearm he holds the pistol with his finger inside the trigger guard. Someone trained in the safe handling of firearms, particularly in law enforcement, would know to treat any weapon as loaded and not handle it by the trigger.
When Allen turns in his gun after his "desk pop" he ejects the magazine but does not rack the slide before handing it over, leaving a live round in the chamber.
When Allen is trying to remember the name of the Meg Ryan movie at dinner, he says it was "She's Got Mail" instead of You've Got Mail (1998) and Sheila agrees.
When Captain Mauch is giving the pep talk at his Bed Bath and Beyond job, he says there is a serial rapist in Crown Heights. He works as a cop in Manhattan, Crown Heights is in Brooklyn.