Dude's shirt changes back and forth from white to blue.
When Postal Dude and Faith have their guns pointed at each other, their outstretched hands pass one another. In one wider shot, their guns are lined up next to each other.
The World Trade Center did not have human window washers, but rather machines that washed the windows automatically.
When the Taliban shoot up the roof of the van, bullet holes appear everywhere on the roof, even over the driver's seat where no one fired a weapon.
After declining Osama's credit card, the guy who sells the "How to Dominate your Worker" merchandise runs the next customers' cards through his machine upside down. They clear.
The "Little Germany" letters cover a "Little Holland" sign that can still be seen through. There's also a typical windmill on the roof.
During the big final shootout, when Zack Ward shoots everyone with the machine gun, the spent casings fall to the ground in slow motion. They're obviously blanks with crimped ends, not empty casings, which would come from live ammo.
In Little Germany, while the female reporter is talking and the camera pans around the dead children, a child in a blue and white checkered shirt is breathing.
On the UK release DVD there is a typo on the blurb which is meant to read 'first they must fail'. Instead it reads 'first they most foil'.
When the postal van is hijacked, two Canada Post mailboxes boxes are visible in background. The story is set in the United States.