Trivia: When they are preparing and listening to the tape you can see a bit of smoke in the air. There had been an extended scene where they had been smoking pot and joking around. However, they used real pot when filming and much of what was shot ended up being unusable as a result. This is according to Bruce Campbell's Commentary to the DVD.
Trivia: The BPRD complex was (according to Del Toro) was originally FDR's secret emergency bunker. The library where Professor Broom dies was the president's office and Hellboy's room (with the big vault door) was his fallout shelter, just in case Germany perfected the A-bomb first.
Trivia: Stay after the credits. There's an additional scene where John goes to visit Chas' grave and leaves a lighter, then as he's walking away you see Chas with wings and he flies up into the sky. (01:54:40)
Trivia: In the courtroom scene, all the people that have turned to color have to sit on the upper level. This is reminiscent of "To Kill a Mockingbird" (1963) where, in a similarly-built southern courthouse in the 1930's, all the "colored people" (African Americans) were relegated to the upper level.
Trivia: When Eric first goes back to his apartment, right after he returns from the grave, it is raining inside the apartment and his movements look an awful lot like the movements he just made in the rainy alleyway. [Not really a mistake, but worth noticing - the filmmakers were forced to re-use some shots after Brandon Lee's death.]
Trivia: Marc McClure, who plays the delivery driver named Boris actually played Anna's (she was then called Annabelle) crush, Boris, in the original "Freaky Friday" (1976).
Trivia: The newborn goo used during Bella's birth scene was made from cream cheese and jelly.
Trivia: A relief carving of Sulley (from the following Pixar film, Monsters University) is visible in the Witch's cottage.
Trivia: David Lynch was disgusted with the elongated cut of the film which includes paintings of the 'robot revolt' back story to the original film, a sub-plot he deliberately omitted. He demanded his name be removed from the credits of the film and replaced with the Director's Guild nom de plume, 'Alan Smithee'. This was done so sloppily, by superimposing Smithee's name over Lynch's, that the credit reads "A ALAN SMITHEE FILM".
Trivia: There is an actual band in Canada called the Wyrd Sisters who tried to stop the November 18th release of 'Goblet of Fire' in Canada because there is a band of the same name in the movie, but they lost their case.
Trivia: Helena Bonham Carter, who plays the grown up version of Jenny (from the town of Spectre), also plays the witch. She was at the time in a relationship with and eventually married director Tim Burton from 2001-2014.
Trivia: Domhnall Gleeson, who plays Bill Weasley, is the son of actor Brendon Gleeson (Mad-Eye Moody).
Trivia: In the scene near the end of the movie, there is a board meeting on the tarmac. The Chairman of the Board is Stephen King who is the author of The Langoliers. (02:10:15)
Trivia: Michael's neighbors last name is O'Doyle, which is the name of the bully kids in Billy Madison who say "O'Doyle Rules."
Trivia: I was an extra on the Highlander Scottish battle scenes and since Scottish weather isn't the most hospitable, all the extras got very drunk on whisky to keep warm. When you see the Scottish charge insanely, it's because we were all drunk, which led to us picking out the wrong weapons and kilts for the next days filming because no one could remember who had what.
Trivia: The vampire's last name was Sackville-Bagg - Bilbo Baggins' relations in The Lord of the Rings were the Sackville-Bagginses.