Factual error: When Professor Broom puts the old pieces of paper together, the text translates to "Graveyard 16", not "Sebastian Plackba 16".
Factual error: During the subway fight, Hellboy rips a payphone off the wall, which sparks as he does so. A phone does not have a voltage source that would be high enough to spark.
Answer: The internal machinery that powers him is clockwork. It needs to be wound like a watch every so often. He releases most of the tension when he fakes his death.
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