Factual error: When the wraiths first invade the stockade, one of the officers orders his men to fire their "rifles". This is the 16th century. They're firing muskets.
Plot hole: *SPOILER* Toward the end of the movie, Ryan Gosling goes to Hopkins' house where Hopkins is tricked into not only confessing again, but giving Gosling the murder weapon, after they are back in court and Gosling is the acting prosecutor. This would be a conflict of interest due to the fact that Gosling is a witness.
Suggested correction: First, the gun that Beachum took from Crowford's house was not the murder weapon. It was Crowford's unfired gun. He only took it out of the fear of his life. Second, Beachum entered Crowford's house with police supervision. If he plays it by the book, Crowford's confession is valid. In that case, supervising officers will stand witness, along with a recording confirming their testimony. Third, Beachum doesn't need the confession anymore. He was amply clear on that matter.
Factual error: The license plate on the blue Ford Taurus is 674-H2T. Format for New Mexico standard issue yellow plates is 123-ABC (three numbers, the Zia sun, followed by three letters).
Revealing mistake: At 39:55, actress Jaime King gets out of the shower, and she has just reached for her robe, and then on the bottom right corner of your screen you can see a bit of the flesh-colored body suit she's wearing. Continue to 40:00 where you see it again. Continue to 40:05-40:09 where you can see it, without slowing or stopping frame. (00:39:55)
Continuity mistake: In the beginning of Part 3, Ryan Reynolds is on a deserted two-lane highway asking Hope Davis for help. She refuses to help, begins to turn and walk away down the double-yellow center lines of the road. In the next shot, we see her finishing the turn and walking on the edge of the road, by the white line (facing traffic). Immediately after, she is shown on the right side of the road, on the other white line (walking with traffic). (01:14:15)
Continuity mistake: When Frylock is watching New Jersey getting destroyed by the Insane-O-Flex, look for a building to the left through the Ferris Wheel. When Meatwad transforms into a building, the fires briefly stop, then turn on again.
Other mistake: The film's set in Seattle but was filmed in Canada. This is evidenced by things like a Canadian red striped postal box as well as cars with Canadian license plates.
Continuity mistake: The two protagonists are having a conversation at a long table. Michael Caine sends a bottle of wine rolling across the table. Jude Law opens it and pours. The bottle label now faces him. After Caine says the line "I've never heard of an Italian called Tindale", Milo hasn't moved but the bottle faces the camera now. There's another subtle change in angle and level of the liquid a bit later when Caine says that his wife would get the "Tindelini" last name. (00:09:20)