Continuity mistake: After Julia sees the vision of Frank being tortured, she walks over to a window and faces it. The scene then cuts to a wideshot, and instantly Julia goes from facing forward, to facing sideways. (00:48:20)
Visible crew/equipment: When Julia sees the vision of Frank being tortured by the cenobites, at one point "Butterball" turns and looks at camera, and you can see a set-light reflected in his glasses for a brief moment.
Continuity mistake: When Frank grabs Julia's wrist/hand in the attic after she tells him to "Keep your voice down!," watch closely. The way he's gripping her wrist/hand changes a few times between cuts. Additionally, depending on the angel, her hand either is or isn't casting a shadow on her face. (00:43:36)
Continuity mistake: The shape of Frank's body changes a few times depending on the scene from when he is resurrected to when he absorbs his first "victim." In some shots, it's an extremely skinny body double when it's doing the weird crawling movements, while in other shots where it's the main actor, his body seems a bit "thicker" and "fuller." When it's the skinny body-double, the shape of Frank's head also changes slightly, and is a bit larger and rounder.
Continuity mistake: After Julia kills her first victim, the amount and pattern of the blood on her face changes once or twice over the remainder of the scene. (Most noticeably, it changes from before she drops the hammer, to after when she backs up against the door).
Continuity mistake: After Julia kills her first victim, she drops the hammer and backs away. As the shot cuts, suddenly, a large blood-stain appears on the victim's shirt between cuts. (It's on his shoulder).
Continuity mistake: When Kirsty leaves the bathroom and encounters Julia after Julia first meets Frank, the lighting on Julia noticeably changes between the wide and closeup shots of her. Her shadow on the wall also changes between the two angles.
Continuity mistake: After the dinner scene, Julia goes up to the attic and the shadow she casts on the door changes twice between cuts. We get a POV shot of her approaching the door, and right before it cuts, we see a teeny bit of shadow appear on the door (from Julia approaching it). It then cuts to a wideshot, and there's instantly a LOT more shadow on the door. Then a few seconds later, the shadow on the door changes again during the closeup of her turning the handle - there's suddenly much LESS shadow.
Continuity mistake: When Bill kisses Julia on the cheek as she's about to step away, he puts his hand on her arm, right under her shoulder. When it punches in to a medium shot from the wide, his hand is no longer there.
Continuity mistake: During the dinner scene, when Julia stands up to leave, as it cuts between her and wider shots of the table, the expression on her face and the direction she is facing subtly changes a few times between cuts.
Audio problem: When Kirsty is flirty with Steve at dinner and he says "So lay down," the audio doesn't QUITE match his lip movements. (Several characters were redubbed with American accents in post. Presumably this is the reason for the inconsistency).
Continuity mistake: When Frank is being resurrected, and his "torso" lurches forward and attaches to the brain, the shape and position of the brain, and the amount of goo on it changes twice between edits.
Continuity mistake: When Frank is being resurrected, when the arms first lift the barely-formed "torso" off the ground and it cuts from a medium to a closeup shot (where we see a closeup of the two little "tendrils"), the amount of goo/slime/blood on the torso changes between shots. A lot of the goo/slime/blood instantly vanishes between cuts.
Continuity mistake: When Larry comes to the attic after cutting himself, the amount and pattern of the blood on his hands/forearms changes slightly when it cuts to the wide, high-angle shot.
Continuity mistake: After Larry cuts his hand, he goes the attic, and we get three closeups of blood dripping onto the floor. Two problems. Larry starts to walk forward at one point, but we get another closeup of the blood hitting the SAME spot on the floor, which makes no sense... it should have dripped in front of the puddle since he moved. Then, Larry walks all the way across the room, and we get a FOURTH closeup shot of blood hitting the SAME spot, even though that spot is a good 12' behind him at that point.
Continuity mistake: When Kirsty first enters the house, she pushes the mattress in the doorway up to squeeze by. In the first shot, it's only about 3-5" over her head... but in the next shot, it's suddenly about a foot higher in the air.
Audio problem: When Kirsty enters the house and the moving man says "My lucky day!" his words don't quite match the lip movements, making it obvious the line was dubbed in post.
Continuity mistake: When Kirsty first arrives at the house in the beginning, she stands outside for about five seconds. If you pay attention, her hair changes when it cuts from behind her, to the front, then back. (In the shots behind her, her hair is going straight down over both her shoulders, whereas in the front-facing shot, it's pulled off to only one side).
Deliberate mistake: When Larry and the two moving men are first bringing the mattress through the doorway and it gets "stuck," the camera placement makes it pretty obvious that the mattress isn't really stuck. There's far too much wiggle room on either end for it to be "stuck." (Obviously it needs to be stuck for the scene to work... but still a weird inconsistency).
Continuity mistake: When Larry goes to get beer for the moving men and Julia walks by them, the directions they are facing and the looks on their faces change slightly between cuts.
Answer: Letting the moviegoers know what happened to him, he was no longer human, but a piece of meat to be butchered.