Continuity mistake: In the scene at the beginning of the movie where the flying vampires are chasing the security guard across the boardwalk parking lot, the positions of his arms as he is running changes back and forth between shots. In the close-ups of the guard's face, his hands are up, holding his hat down on his head. In the wide shots, his arms are down at his side. (00:02:45)
Continuity mistake: In the secret covenant, the amount of blood on Eve's white top decreases when Olivia the vampire doctor examines her wounds. This is most noticeable under the collar. (00:34:20)
Continuity mistake: When the group of girls first pulls up to the gas station and talk with Barney, the shadow cast by the sign is much longer than moments later when they leave. (00:11:15 - 00:12:50)
Continuity mistake: The last two pictures on the left on the wall going up the stairs change continually throughout the movie, at least 10 times. (00:24:35 - 00:26:35)
Visible crew/equipment: When Dr. Loomis arrives to the gas station the boom mic's shadow is visible on the ground. (00:19:02)
Visible crew/equipment: After they've killed the snake, Alice says "Is it dead?" and as the camera pans up, the boom mic's shadow is visible moving across the wall, directly over Ned's head and the red box. (00:26:05)
Visible crew/equipment: When Mia first does the ritual, you can see the boom mic on the bottom right corner. It hides in the dark corner, but if you look carefully, you can see it come in the shot. It's easier to, depending on how dark your screen is. (00:20:40)
Continuity mistake: During the whack-a-robot game, a big chunk of the broken robot lies on the counter, but it disappears a shot later.
Continuity mistake: When Burt is hiding in the bulldozer scoop, Grady looks down at him from the top of the oil tank and we see that Burt has his knife in his hand. However, in the next shot, we see him pull the knife out of its sheath on his leg.
Revealing mistake: When the sea creature appears and the raft overturns, the people falling are very obvious stiff dummies. One even falls downwards and its two feet stick up from the water.
Visible crew/equipment: When the martian space ships first appear you can see the wire suspending the models. You can clearly see the wires every time you see a martian or martian space ship.
Visible crew/equipment: When Charlie is in the ventilation system and says, "I could use some help here," the boom mike briefly pops into the picture. (00:44:40)
Visible crew/equipment: When Scott is finally killed by the giant scorpion, the hand of the puppeteer is seen on the left.
Continuity mistake: When Blade gets captured and stabbed in the room where the "Vampire Bible" is, he is not wearing an ear piece. In the next shot, he is. (00:51:45)
Continuity mistake: After Gen. Perez pushes the stacks of money towards Elgyn, they are right on the metallic edge of the table when the general offers a drink to Elgyn. In all of the following shots, the stacks have moved and are further in on the table, not on the metal anymore.
Continuity mistake: When Jason kills Lizabeth, the first shot shows Jason with his feet on either side of her head, but in the next shot, his feet are together and away from her head. (00:14:35)
Continuity mistake: When the tentacle monster rips out a chunk of Norm's chest, a large spray of blood splashes on his right-side jaw and cheek. In every subsequent shot of him, this blood is gone and his jaws are completely clean. (00:26:30)
Revealing mistake: Ryan Reynolds is wearing red-eye contacts. You can see the whites of his eyes around the red circle of the contacts in several scenes - most noticeably, right after the home movie he's watching down in the basement melts.
Suggested correction: Not a mistake. Ryan Reynolds actually had bloodshot eyes from being awake for nearly two days of filming. He stated it in an interview for the movie.
Revealing mistake: When Shooter pins Mort against the tree with the shovel, you can see that it's a rubber shovel because it's bending around Mort's neck. [Mentioned on commentary]. (00:40:45)
Continuity mistake: When Vic and Josh are urinating on the slate, Vic holds it in front of him and the writing on it is perfectly legible, but when it shows him holding it out, it is runny and you can't read it.