Hellboy: 20 Easter Eggs And References Explained
4. Crown Of Bethmora
Hellboy's climactic transformation at the end of the film - while not perfectly justified - manages to both look cool, and also references a pretty major part of the comics.
The 'true' demon form of Hellboy is referenced repeatedly throughout the source material most crucially due to it revealing one of his potential destinies - through the crown of the apocalypse that appears on his head when he uses his more demonic powers.
Although it isn't directly explained within the film, the crown - and Hellboy's rejection of it - is absolutely crucial to the storyline, as otherwise Hellboy's fate is solemnly sealed as the bringer of the end of days.