Several of the bodies hanging from the rafters in Channard's house that Julia had killed were obviously mannequins. Real dead bodies would hang heavily and slack from their bonds but at least two that I could make out weren't weighing on their ropes at all; they were posed, standing dummies.
When the Cenobites appear in Dr. Channard's office, the curtains are ripped away from the window. You can see the string that rips them away.
When Dr. Channard is being turned into a Cenobite, his tie disappears in some shots.
When Julia shuts Kyle into the room full of hanging bodies, she begins to kiss Kyle, then starts to suck out his blood. After she sucks all his blood out, between shots the amount and position of blood over her lips and chin, changes.
When Julia takes the cigarette from the doctor in the room with the mirror, you can see, if you look closely, that there is no blood on the cigarette. But, the hand she has the cigarette in left some blood on the hand of the doctor.
When Julia first emerges from the mattress and is scrabbling on the floor, you can see the body double is actually wearing a thong.
When Browning lies down while cutting himself, the mattress under him is dry and his blood is only smeared over his chest. Yet when the shot cuts to Channard and back, the mattress has suddenly become utterly soaked in Browning's blood.
In the scene where Kirstie is in Hell searching for her father, she is running up and down Hell's corridor's, becomes winded and stops. As she does so, she slaps herself against a concrete corridor wall; when she does this, you can see that the "concrete" wall looks more like a rubber covering, as it moves with her.
Any time when the two girls are in hell's corridors and running around, you see these corridors as stone walls, yet whenever they back up against one of these walls, you can clearly see they are merely rubber sheeting overlayed on a framework as the rubber sheeting bends and contracts very clearly.
When we see Julia in Channard's house, she is dripping blood, as she is skinless. From where she is standing, she would have had to walk across the room, dripping blood, but the carpet is very clean, excluding the area where she is standing.
In the scene where Channard kills the original Cenobites, the collar of Pinhead's outfit undergoes visible changes. First it leaves his throat exposed but covers the rest of his neck. After Channard turns him back into a human, the collar then covers his entire neck. Finally, the collar completely disappears a second before Channard slashes Pinhead's throat.
When the policeman asks Kirsty at the beginning who came when she solved the box she says the Cenobites; she had no way of knowing what they were called. Frank only told Julia; Kirsty didn't hear it anywhere and the Cenobites themselves didn't tell her either.
The two uniformed officers are dressed like US street police and carry guns. UK police are generally unarmed.
When Browning is cutting himself on the mattress, in one shot his right shoulder is covered in blood, but then in the next close up of him, the blood has gone.
After Tiffany solves the box and it closes itself, all the doors to Hell should have closed up again too as the closing of the box means the closing of the doorways; it happened in the first Hellraiser when Frank died the first time and Pinhead closed the box so they could return to Hell.
When Frank came back in the first film, he was little more than goo on bones but when Julia comes back she is much more whole. True, she had a lot more blood to use than Frank to begin with, but it still took Frank three bodies' worth of blood to look the way she does when she comes back.
When Frank grabs Kirsty when she finds him in the hell room, he grabs her and throws her into the stone wall. As she is thrown into the wall it bends like rubber and buckles under the impact.
Despite being set in Britain, the detective that visits Kirsty is from the local homicide division. UK police forces don't have homicide divisions.
At the beginning of the movie, policemen are inspecting the deceased Rory's house to retrieve the bloody mattress for Dr. Channard yet at the end of the first Hellraiser, the house completely collapsed.
The mover shouldn't have been pulled into the mattress because he didn't bleed onto it, which is what was required before, for Julia to come back.
After Julia punches her arm into Franks' body and grabs his heart out from his skinless body, in the wideshot after she has grabbed his heart out her face is clean, but in the next closeup there is suddenly lots of blood on her chin.
When Pinhead becomes human again and gets his throat slashed, you can see the black net-material behind the fake skin that provided the blood.
When Tiffany almost falls off of the ledge, you can briefly see a wire on her back.
When Dr. Channard is looking through the sliding panels at the really crazy patients in the padded rooms, there is a man with a tattooed head wielding a crucifix. The fact that he is in a padded room means that he is a danger to himself and would not be allowed a metal tool that he could hurt himself with. Also, the door on the inside isn't padded like the walls which it should have been.
When Kyle goes into the dead-body room, there is a shadow of a hanging dead person on the wall next to him. The shadow of the open door on the wall on the other side of him shows that the shadow of the body shouldn't have been there as the light would have to have been coming from the very far wall. When Kyle is looking around you can see that the only light source is the high windows on the left side of the room.
When Julia emerges from the mattress and kills Browning, the mattress becomes completely saturated with blood. Then when the mover comes to take it away at the very end, there are patches where the mattress is clean. Then again, when he is pulled into it and his friend comes into the room, it is saturated again.
When Kirsty is confronted by the Cenobite doctor, Dr. Channard, there is a huge gust blowing towards her. If you look behind her, there is a suppossed stone wall, which appears to be flapping in the wind, revealing it is merely a fake set wall.
When Tiffany goes back to retrieve the diamond shaped box from Julia's grasp, the position of Julia's fingers around the box change between shots, as Tiffany reaches down to grab it out of her hand.
When Tiffany almost falls off of the ledge, the ledge wobbles violently when she grabs it.