TedStixon

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.

TedStixon

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.

TedStixon