Question: Little Adam is looking in a grass-filled jar at the beginning of the movie which has a label on it that says "Curtis". At the very end of the movie, grown up Adam (as a sheriff) has a man working for him whose name is Curtis. What is the connection here? There is obviously one.
Answer: According to the Director's Commentary with Bill Paxton, the "pet in the jar" was a millipede and was named "Curtis" by Matthew McConaughey simply enough after Bill asked, "What should we call it?" Later when the other Curtis appears Paxton comments that "This guy's name is Curtis and people go 'Wow, why is that guy's name Curtis and the pet Curtis?'" But he fails to actually answer the question. In the Producer's Commentary they also reference the dual names, but again have no explanation other than to point out the fact that it seems to catch the attention of viewers.
Answer: I think it is spurious. The two may appear to be related but are not.
Chosen answer: Paxton is obviously mentally deranged so he can call anyone a demon and find a way to justify it.
William Bergquist
This answer is entirely incorrect. If you watch the film, you realise that it is only Fenton's belief that his father is insane. In the reality of the film, everything his father has told him is true. He is in fact a "demon killer." Since there is no explanation in the film as to what actually makes someone a demon, it's safe to assume the angel knew Fenton would grow up to become a serial killer. The father refused to believe his own son would be a demon, and so tried to force him to "see" the truth.
It really isn't "in the reality of the movie" - it is in the dad's psychotic mind (his warped sense of reality). What sane father, for example, would subject his children (preadolescents at that) to chopping people up with an ax, have them help dig graves and bury those killed, lock his 12-year-old son in a "dungeon" with no food and only one cup of water a day, check on his son after a week but nail the door closed again for another (apparently long) period of time? And I don't think Fenton became a serial killer - Adam was the serial killer (maybe of demons in his warped mind). The father seemed to assert that Fenton was a demon because he was not supporting him in killing people ("destroying demons"). Why didn't the father view Adam - who could be viewed as killing his own mother during childbirth - as a demon? Adam, being younger and more impressionable, agreed with the father but was also told they were like "superheroes" - what young kid could rationally discern the difference?
KeyZOid
The cartoon shown on TV ("Davy and Goliath") offers additional evidence that the father was not destroying demons. "Davy" asks his father about God, and his father tells him that "God doesn't make you do anything" and wants you to decide. Even IF God or the angel sent someone a list of demons to destroy, it would be up to the person to decide whether or not to destroy the people. I know that the purported acts of the people that were killed were revealed when the dad (or Adam) put his hand (s) on them, and that viewers were then supposed to believe that they really were destroying demons, but the view that they were just hallucinating is still valid.
KeyZOid
I think the movie allows the viewer to make his/her own conclusion - is the father really destroying demons or is he a cold-blooded murderer? There is sufficient reason to believe the father had a psychotic breakdown or something similar and, instead of destroying demons, was a serial killer. There was no evidence of any others being chosen by God to destroy demons, no indication that the world was coming to an end, and no reason to murder the sheriff who was leaving and said he didn't believe one bit of what Fenton told him about the killings. Besides, wouldn't God protect the father from the sheriff if He protected Adam from being detected by the FBI agents and cameras? For what it is worth, I disagree with the comment by Jason below and think your view is more accurate.
KeyZOid
There are several important factors that show the father (and son) are actually fighting demons: The "help" they frequently receive, like ALL of the surveillance tapes not showing Adam's face when he's hunting a demon (This can hardly be dismissed as coincidence, as they all look fine except wherever Adam's face would be visible), the FBI agent at the end who inexplicably can't describe Adam and doesn't recognize him when they meet again, the fact that the victims are stunned after the father or Adam touches them with a bare hand to reveal their sins, etc.
I'm aware of all of those things, but videotapes used to do that - maybe if the FBI agents tried fixing the alignment his face would show. Adam looked different to me, too - his hair looked redder than when he was at the FBI office. Of course victims would be stunned and scared when a lunatic grabbed them. I do understand what you are saying, but I still don't think it is enough. Surely there were far more "demons" out there; the number of killings was relatively small. And, again, Davy said that God doesn't make anyone do anything - He wants the person to decide.
KeyZOid
The point with the video tapes is that they say ALL of them are like the one, with the image only messed up across his face, and only when his face is visible. I suppose this is just an agree to disagree issue. You don't see these things as enough, while I see them all combined as more than enough. Interesting discussion of a good movie either way.
I was thinking of writing something like that to you! And now I can agree with something you wrote!
KeyZOid