One of the best moments in There Will Be Blood comes when oilman-misanthrope Daniel Plainview first meets preacher Eli Sunday, after having already met and done a business deal with Eli's identical twin brother Paul earlier in the film. The camera lingers on Plainview's face as he examines Eli, trying to ascertain whether this is some kind of scam and if the person he's talking to is really Paul, passing himself off as the new brother for some nefarious reason. Some have speculated that this scene and the whole identical twin device P.T. Anderson uses has a lot of resonance because it shows what a disadvantage Plainview typically finds himself in when trying to know the mind of another person. (It's a problem that he deals with again in the film when a man arrives claiming to be his long-lost brother.) But it seems that we may be reading too much into it -- in a new half-hour Fresh Air interview, Paul Dano, who plays both Eli and Paul, says his casting in the roles of both brothers had a much more mundane genesis -- another actor was originally cast as Eli and then let go.
"Somebody else was cast in that role and replaced with you?" the NPR interviewer asks Dano, to which he replies "Yeah. For what reason I'm not sure. I don't care to know, or I didn't want to know." Dano says that the unknown actor had already been filming for a short while when Anderson approached him about taking over the role and he had less than a week to prepare for the part. "We looked at some scenes and talked about the part a little bit and he said 'I'd like you to do this part' and they'd been filming for a little bit already, so I said 'Okay, that's great. It's a little bit of a shock.' And he said 'And why don't you still play the Paul part and we'll just make them twins?'"
Dano also talks at length about how he views Eli, saying that "he's somebody who I think made himself up. He invented himself. I think he's quite a bit of an actor. He created this persona at a very young age once he saw what religion and his curiosity with religion could do for him." If you want to hear the rest of the interview, and I recommend it, get yourself to NPR and click on the recent Fresh Air programs.