Continuity mistake: When Hellboy punches the car in the street, watch closely: he knocks the bumper off, it moves in the direction of the car, yet it never hits the ground. (00:32:30)
Continuity mistake: When Rasputin is talking to the professor about the evil in him, his hand ripples. From the front, his small finger is mostly straight, but in the shot behind, it's mostly flexed. Cut back and it's straight again. (01:17:40)
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.
Continuity mistake: In the chapel at the end, Ilsa punches Myers and looks down to her right at him. Next shot is over Hellboy's shoulder, and she's still looking down in the background. Cut back to her for several lines and she's looking up and to her left. (01:41:00)
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,.
Continuity mistake: When Hellboy chases Sammael into the subway, in one shot, he's slightly leaning to his right. In the next shot, he's leaning to his left with no time to change. This has nothing to do with the camera angle.
Continuity mistake: When Hellboy throws the Nazi guy into the spike pit, a bunch of objects also go in as well. In several shots, they disappear or change position.
Continuity mistake: In the Sammael chamber, the room is a big area with barely anything around the centre. Then Liz tells Myers to run and suddenly there's a big rock for him to hide behind.
Continuity mistake: When Hellboy is captive at the end, he doesn't have the Professor's Christian necklace. A few shots later, he suddenly does.
Continuity mistake: When Hellboy is fighting the big tentacle thing, he falls and starts to get up. In the next shot, he starts to get up again.
Continuity mistake: When scraping the snow off thee wall at the start, the amount of snow changes drastically and instantly. The lines of the engraving are clear of snow instantly. (00:14:30)
Continuity mistake: At the very start the priest holds up a crucifix and says the men will need them. The way the crucifix is held changes instantly. (00:02:00)
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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