Hellboy II: The Golden Army
- Guillermo del Toro turned down a film version of the X-Box game series "Halo", "I Am Legend" and "Harry Potter and the Half-Blood Prince" in order to work on this sequel.
- Revolution Studios was originally set to produce this sequel but had to pull out once Sony decided they no longer wanted to fund Revolution Studios.
- Rupert Evans (Agent John Myers from the first film) couldn't reprise his role due to his casting in a stage version of Kiss of the Spider Woman (2007) in London and was written out of the sequel.
- Ron Perlman was offered the role of Piccolo in Dragonball (2009), but turned it down in favor of reprising his role of Hellboy.
- In September 2004 del Toro expressed interest in making Hellboy into a trilogy with Mignola, with the first sequel slated for a 2006 release.
- Thomas Kretschmann was the first choice as the voice of Johann Kraus, but Guillermo del Toro was not satisfied with the result, and subsequently brought in Seth MacFarlane.
- Christopher Lee was, reportedly, offered the role of King Balor, but had to turn down the role.
- Universal Pictures acquired the project in 2006 and slated it for a Summer 2008 release.
- Neil Gaiman spent several days on the set to get pointers on directing from del Toro for use in his own upcoming directorial debut, Death and Me.
- The movie mentions Bethmoora, a city in the fiction of the early 20th century visionary writer Lord Dunsany. Also note that the Golden Army is hidden in Ireland, Dunsany's homeland.
- The enormous female statue shown in the auction scene is a representation of the Venus of Willendorf.
- This is the first movie to be filmed in the new Korda Studios in Budapest, Hungary
- In October 2006, del Toro shared his plan to recreate the classic versions of Frankenstein, Dracula and The Wolf Man in the film.
