Revealing: When Professor Broom's coffin is being carried, it is raining, and the camera is overhead, no rain falls in the centre of the picture, as the camera is in the way.

Deliberate "mistake": Every time someone gets skewered through with a blade in this film there's never any blood on the blade afterward.

Other: When Kronen is getting ready to kill Broom at the beginning, the Sargent shoots Kronen. One shot hits Kronen's mask and the bullet ricochets off of it, yet there is no dent in the mask.

Continuity: 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: At the museum, if you watch Kroenen slice the statue open in slowmo, you can see that the cut doesn't appear until after he is finished with the motion (it should appear gradually during the cut) and shows up in the wrong place (it starts below the statue's left hand, but he sliced above it).

Continuity: When Liz goes to tell Hellboy that she is going out with Myers, her arms change from at her stomach and shoulder to at her sides between a shot from behind and the next front shot.

Continuity: 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.

Continuity: In the scene in the subway station when Hellboy is fighting Sammael, he grabs the monster by the tongue and swings him through a large window. Sammael jumps down and is hanging in the subway tunnel, but can't get away because HB still has a hold of his tongue. The train hits and kills Sammael. But when the shot goes back to Hellboy, the tongue, which should still be attached to his hand, is gone. He's holding his hand out as if it's still there, but I guess they forgot to add it later in CGI.

Continuity: 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.

Continuity: 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.

Continuity: 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.

Revealing: When Sammael throws Hellboy at the subway station into the upper level, slowmo reveals that the wires carrying him are pulling on Hellboy's jacket at the shoulders.

Continuity: 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.

Revealing: When Hellboy is filing down his horns with the small razor/sander contraption, you can tell the small sparks coming off are not coming from the contact of his horns and the sander, but rather are coming right out of the sander, revealing it is a prop.