Revealing mistake: When Castor is pushed into the blowing heat from the plane engine by Sean and is thrown back, the man that lands against the grill is so obviously the stunt double; he has a different hair cut than Castor and really doesn't look anything like him.
Continuity mistake: During the cemetery scene where they visit the son's grave, you see a wide shot of them walking between the stones. There are leaves on the trees and neatly trimmed grass. When we see a close up of the stone and the plaque in the ground, a hand reaches down to brush the leaves off so they can read it, and there are dead leaves all around - but there were no leaves on the ground in the wide shot.
Visible crew/equipment: When Buzz and Wanda stand in the outer room, in the first shot, the camera pans around and faces the agents' TV, showing the video feed of Pollux in the interrogation room singing about his tiramisu. On the agents' TV screen, the reflection of the crew's rather large black square screen is visible (on a stand) in front of the windows (to block window light and view of the crew/equipment) and just as the camera faces the TV head-on, a crouching crew member begins to stand (seen at the left side of their TV screen). (00:59:05)
Revealing mistake: At Erehwon, Sean (as Castor Troy) is given steel magnetic boots to wear, for the prison's important security feature. There is a close-up of these heavy duty boots during his 'exercise'. Then, when he is taken to the clinic there is another close-up, and there are a number of changes to the boots style. More importantly, one of the side "bolts" has fallen off, revealing that it was merely glued on the prop boots.
Revealing mistake: Just as the red speedboat heads toward shore, before it crashes, the white and red truck cranes are on the dock and the white crane arm is angled backwards over the dock. In the shot facing the speedboat, as it explodes, that crane arm is now angled the opposite way, over the water, since it was used in the stunt.
Factual error: In the scene in the hall where there are is a circle of mirrors where Castor and Sean engage in a shootout, there is a mistake as the FBI agent fires at Castor. The FBI agent is holding an M16 or M4 assault rifle with an M203 40mm grenade launcher. He fires two consecutive shots within a second of each other. This is impossible as the M203 attachment only holds 1 shell at a time and would take at least 5 seconds to grab another round and reload and fire again.
Continuity mistake: When Castor (as Sean Archer) grabs the speargun shaft before it can unload, he takes a piece of glass and begins to cut his face. The broken glass has a small circular piece missing from the edge, but from a different camera angle that small piece is more intact than the previous shot. (02:09:15)
Continuity mistake: When Castor Troy (as Sean Archer) says, "Every time you'll look in the mirror, you'll see my face," he proceeds to cut his face. The first cut he makes is straight down the side of his right cheek (viewer's left) and later that cut is curved and closer to his nose. This may appear to be a mistake at first glance; however, Castor's facial expression is different in the two images. When he made the cut, the cheeks were pulled away from the nose; in the second photo, the muscles are relaxed, moving the cut closer to the nose. (02:09:15)
Continuity mistake: After the surgery, when Sean (as Castor Troy) breaks the center mirror of the tri-fold mirror, what remains are the two side mirrors and white backing within the center frame. When Tito grabs him as he starts cursing, in these close-ups the reflections seen are as if all three sides are still intact. (00:37:15)