Quiz

As the Angel of Death, Doug Jones could only see out of the crack across the mask he wore. Also, the mechanical wings he was wearing weighed about forty pounds. Doug was originally supposed to walk around the set, but when it was discovered that he could barely stand, they instead hung him from a wire. This is why The Angel of Death floats.

The Angel of Death's voice is done by Doug Jones doing each line twice, once in a higher pitched voice, and then in a lower pitch, and then the two takes were blended together.

David Hyde Pierce did the voice of Abe Sapien in Hellboy (2004), while Doug Jones played the physical part. For this movie, Jones also does the voice. The reason is because the producers hoped Pierce's name would make the first movie a box-office smash. But he refused to be credited, because he felt Abe Sapien was Jones' work, and as such, did no promotions nor interviews, nor even attended the premiere.

Peter Jackson approached writer and director Guillermo del Toro to direct Halo, and even though del Toro considered it, he turned the offer down so he could direct this sequel. Also, del Toro turned down Io sono leggenda (2007), Chiamata senza risposta (2008), and Harry Potter e il principe mezzosangue (2009) for the same reason.

The outline of the movie revolves a great deal around Ireland and Irish mythology: Nuada is the name of the first King of the mythological Tuatha De Danann people. The mythological Nuada bore the epithet "Silverhand" because, having lost his arm in battle, he wore a functioning silver arm. In the movie, Nuada's epithet is "Silverlance", and Nuada's father, Balor, has a mechanical arm.

Blake Perlman: The female reporter seen interviewing Hellboy outside of the auction house is Ron Perlman's daughter.

Santiago Segura: The "Distinguished Customer" in the auction scene is a frequent player in movies directed by Guillermo del Toro, and voiced Johann Krauss in the Spanish dubbed version.