Continuity mistake: In director's cut dvd edition, toward the end of the movie, when Hellboy hits Kroenen in a head, and says, "You killed my father, your ass is mine," Kroenen's left side of a mask changes from being damaged to intact, than damaged again from different angles. (01:43:20)
Continuity mistake: At the end of the movie, when Hellboy and Liz are talking and Hellboy says, "Hey, you on the other side, let her go...", he raises his head and their heads are close to each other. When it cuts, their heads have moved further away from each other. (01:52:30)
Revealing mistake: When Hellboy drops the giant cog on Kroenen and kills him, there's a bizarre mistake. As the cog falls towards camera, it sort of half-rotates in mid-air and you can see Hellboy in one of the little gaps for about one second. And you can see him standing above... holding the exact same giant cog that is currently falling towards camera. According to the YouTube series "VFX Artists React," it's likely the result of the VFX program just looping the footage to insert behind the cog.
Factual error: When Professor Broom puts the old pieces of paper together, the text translates to "Graveyard 16", not "Sebastian Plackba 16".
Other mistake: In the scene where we see Professor Bruttenholm talking to Myers about Abe's origins, we see the professor pick up what he specifically describes as "rotten eggs" from an open bowl and place them into a tube. The eggs have been sitting out in the open the whole time, but Myers only reacts to the smell once Broom picks them up.
Revealing mistake: In the scene in the alley behind the museum where Hellboy first encounters Rasputin, Sammael has its tongue wrapped around Hellboy's arm. When Myers enters and shoots at Sammael, look closely at Myers' hands. Not only does the gun fire without him pulling the trigger, but the gun does not even recoil.
Continuity mistake: After Hellboy falls on the dumpster and sees Rasputin walking toward him, there is a smear of blood on HB's lower lip. It cuts away for a second to show him pick up his gun, and when you see Hellboy again, the blood is gone.
Continuity mistake: At the end when Hellboy is carrying Liz off the altar she hasn't got a top on. Later after Hellboy kills the behemoth she has got a top on.
Continuity mistake: At the end of the movie, when Rasputin is about to take away Liz's soul, the shot is over Rasputin's shoulder with Hellboy's front in view. We can see Rasputin's hand move from above Liz's chest to her jaw as he bends over. Then the shot changes to Rasputin's front. In this shot, the hand is back above Liz's chest and is moving to her jaw again.
Continuity mistake: When Kroenen slices the statue, the cut where the reliquary splits in half isn't close to any of his hits; his hits are toward the upper half of the statue.
Continuity mistake: In the scene where Hellboy and his group arrive at Graveyard 16, a shot from farther away shows the graveyard in the background and in the foreground are the 3 vehicles in which they drove up. The two smaller vehicle's roof, hood and windshield are already covered in what looks like about 1 cm of snow, although they just arrived. Such light and dry snow that appears to be falling in the scene would have been blown off the car while driving, and a layer that thick takes a lot longer to develop.
Continuity mistake: In the final scene between Hellboy and Liz, when he is telling her what he said to bring back her soul, the shots change several times between one of her face, and the back of Hellboy's head, and vice versa. Every time we see Liz's face, she is looking up into Hellboy's face, but when we see the back of her head on the interspersed shots, her head is not inclined upwards at all.
Continuity mistake: When Kronen cuts open the statue in the museum, he in only holding one of his swords. The guards come rushing in and Ilsa says, "get them." Kronen turns and is now holding both of his swords.
Revealing mistake: When Hellboy is running across the path that's being destroyed by the massive pendulum like hammer, at one point he starts to run and you can see he's floating above the rocks as they fall, most likely due to the harness keeping him from falling.
Factual error: During the subway fight, Hellboy rips a payphone off the wall, which sparks as he does so. A phone does not have a voltage source that would be high enough to spark.
Continuity mistake: In the beginning, when you first see grown-up Hellboy, you can see his legs, and like the comic, the calves are skinny and he has hoofs rather than feet. Yet in every other scene his calves are much bulkier (big enough to fill his pants) and he has human feet which he wears large boots on.
Other mistake: During Hellboy's second fight with Sammael, they crash through the ceiling of a subway station, causing panic. While most of the extras are scattering in terror like normal people would, in at least two different shots, you can see a female extra with dark hair who not only looks completely disinterested, but is moving at a slow, leisurely pace, staring down at the ground as though this is commonplace. In fact, it almost looks like she's smirking in one shot. Possibly the world's worst extra.
Continuity mistake: Manning and Hellboy are in the tomb tunnels when Manning brushes the back of his hand against the blades in the walls, but later he shows the wound to Hellboy and this time it's on the tip of his finger,.
Revealing mistake: During the scene in which Rasputin is resurrected, at one point, Ilsa wipes some snow off a wall then checks her book to see if she can match a symbol. When she opens the book, some snow lands inside of it... and it is incredibly obvious that the snow is fake. It looks like pieces of torn up paper.
Character mistake: Tom Manning criticises Hellboy for using a lighter, (correctly) telling him to use a wooden match instead. But he then lights a match and immediately puts it to the cigar, instead of waiting for the sulphur to burn off and using a pure wood-fuelled flame to light it. He's not as well informed as he thinks.
Answer: The internal machinery that powers him is clockwork. It needs to be wound like a watch every so often. He releases most of the tension when he fakes his death.
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