Revealing mistake: In one shot when the boat is pulling away from the waterfall, you can clearly see that the shot is the same one they used earlier in the movie. The water from the waterfall now is going up the cliff! They have just put it in reverse.
Revealing mistake: When the killer is attacking Cici on the balcony, you can see blood on Cici's back before she is even stabbed and both times she is stabbed, the knife that comes out of her back has no blood on it. (00:33:20)
Revealing mistake: When Sarah is making her way to the baby Stego, just before she gets on her belly and crawls closer to it, you can see the kneepads she has on.
Revealing mistake: When Hillard throws the basketball at Ripley, you can clearly see the white tape on Ripley's hand which was used to catch the ball. (00:23:10)
Revealing mistake: When they get Renn back into the room after he has been shot in the face with something acid-like, the smoke comes from behind his head. Not his face.
Revealing mistake: When Andy and Claude are fighting each other in the train, during several shots, you can see Claude wearing gray briefs.
Revealing mistake: When the killer is dragging the girl's body with the meat hook, you can easily see that it is a doll. (01:18:45)
Revealing mistake: When the main character has a cigarette in his booth, smoke rises before the cigarette is lit.
Revealing mistake: In the scene where Sam Neill has set the bomb to blow up the rescue ship, Laurence Fishburne comes running up to the sealed door of the Event Horizon whereupon it shakes back and forth like a stage door would.
Revealing mistake: During the final battle in hell, when the army of Spawns rise up, there are some small errors to look for. First, during a few shots where the army is closer to camera, you can see the CGI army becoming "pixely." Also, you can see at least one of the Spawn floating in the air, not standing on the platform with the rest of him. Problems with the CGI rendering/animation.
Revealing mistake: In the scene, when the bug (actually another Kothoga monster) run out from the box that Margo has opened due to strange noises, there are visible wheels from the puppet of the bug. (00:48:40)
Revealing mistake: Whilst Mima is opening the letters, there is a shot where she is sitting on her bed in the foreground of shot, and the TV is playing in the background of shot. On the shelf below the television is a game console with two controllers on top of it. The animation for the controller on the right is very weird. The right side is drawn longer than the left side, and its positioning on top of the console makes it appear as if it is hovering above it. (00:10:47)
Revealing mistake: When Jack is melting after being showered with acid, at one point, there's a very obvious cross-dissolve used to blend two shots into one as Jack is reduced into a skeleton. It almost works, except suddenly, the snow around him is slightly different. (Some impressions into the snow and whatnot appear during the fade that shouldn't, as does a few pieces of debris.)
Revealing mistake: After the Djinn escapes and there's an explosion in the lab, you can see some stuff on the ground that looks like it's on fire. The objects are not actually burning, the fire is being produced by a burner. There's no smoke from the objects, which is a dead giveaway that they're not actually "on fire." (00:18:15)