Revealing mistake: Before Derek punches the side of the wall, you can see the weakened area of the wall before impact. Look at the color difference.
Visible crew/equipment: When the first car seen in the movie stops, the camera rig can be seen reflected in the hubcap.
Continuity mistake: At the end the guy is watching the video of the man that shoots himself in the chin, blood and bone go everywhere, then it shows the guy and girl walk in but there's absolutely no blood. They would have definitely noticed it.
Continuity mistake: By the end of the film, we realise that the Djinn (in this case an invisible and shape-shifting earthly entity of Islamic lore) has staged most of the film's events as a mass illusion. Meaning, the Djinn is a deceiver and can lead humans into dangerous and even deadly situations, but the Djinn cannot perform physical miracles (or else the whole movie would end almost as soon as it started). At the story's climax, the lead characters, Khalid and Salama, end up in the 62nd-floor penthouse of a luxury high-rise, where Khalid drops Salama to her death from the penthouse balcony, just as the vengeful Djinn intended. However, only minutes earlier, we see that the high-rise building is actually still under construction, and it's stated that the building is months away from completion (its main entrance and plate glass have not even been installed). The Djinn only created the illusion that the building was completed to deceive the lead characters. In reality, without electricity and functioning elevators and hundreds of feet of completed stairwells, there was no physical way for Khalid and Salama to reach the 62nd-floor penthouse suite of the high-rise for the climax scene, even if they were being deceived by illusion.
Revealing mistake: After Alex shoots the intruder in the head, killing him, a couple of shots later you can see his chest slightly expanding and contracting, showing that the actor was still breathing.
Continuity mistake: After the fake movie intro, the two guys drive to a secluded place where their drop is supposed to happen. "Cheno", the one in the driver seat, has the right hand down his side and the left hand on the right side of the steering wheel in a pretty unique position. But in the reverse shot, it's his right hand on the wheel. (00:03:00)
Continuity mistake: Notice how Julie pumps her shotgun twice within a few seconds in the lab without once firing.
Other mistake: In final 14 minutes, the greys are attacking the house. Several screws are "unscrewed" from the plywood. The first two are turned the wrong way, and the sound effect is of tightening. (01:23:54)
Continuity mistake: Our group of jewelry thieves are on their way to "Zugarramurdi" in a stolen taxicab. The "green soldier" Antonio began to wash the color from his face. Nevertheless you can see, depending on the camera angle, that the green color is sometimes seen on his nasal bone and sometimes not. (00:20:55 - 00:21:30)
Continuity mistake: Radha Mitchell is giving a press release at the beginning of the movie. There are many microphones in front of her in rows. In the front row, from her left, are orange, black and blue microphones. In one shot from the front, another black microphone appears next to the blue one. (00:03:35)
Revealing mistake: Not bad digital effects for a combination "Predator" and "Jurassic Park" monster movie, except that the dinosaurs don't cast shadows about half the time.
Character mistake: When Joan is searching the web looking for information on what monkeys eat, there is a section on the screen that reads "The diet of monkeys varies form fruits, leaves." Obviously the correct word for this sentence should be "from" not "form." (00:36:21)
Character mistake: In the scene discussing the provenance of the mirror, the girl stated that Sherman marched to the sea in 1865. It was actually 1864.
Factual error: Near the end, Zoe and Trey battle to the death, Zoe armed with a tomahawk and a knife, Trey armed with a Husqvarna chainsaw. During the battle, Zoe manages to amputate Trey's right hand, with which he was gripping the chainsaw's safety release and trigger (as his left hand gripped the support handle). Bellowing in pain, Trey continues swinging the chainsaw by its support handle with his left hand. Lo and behold, the chainsaw is somehow, miraculously, still revving in-and-out, which is only possible if the safety release is continuously depressed with the palm of the right hand as the fingers rhythmically flex to squeeze the trigger. Of course, with all major tendons in the wrist severed, an amputated hand cannot grip or flex or squeeze anything.
Revealing mistake: When Brooke arrives at the camp to drop off Steph and Chrissy, Chrissy leans out of the car and vomits, but you can see that she's not really vomiting, and is using her hand to cover up the special effects tube.
Other mistake: Throughout the film, you can frequently see many people's faces blurred, phone numbers blurred, store-fronts blurred, etc. This is because the production could not afford the rights to show these people, places and things, and simply blurred them out.
Revealing mistake: When Charlie and Lindsay are having sex, almost when they're done, a horse gets into the bed. The horse disappears too soon.