Family, greed, religion, madness, and milkshakes came together in unexpected and jarring ways in There Will Be Blood, Paul Thomas Anderson’s sprawling tale of a wealthy oilman named Daniel Plainview (Daniel Day-Lewis) who uses his cunning and charm to convince a small California town to let him drill their land for oil in the early 1900s. His manipulation tactics work on all but one member of the community: Eli Sunday (Paul Dano), a young preacher who proves to be a surprisingly deft opponent for Plainview.

On the 10th anniversary of the movie’s release, we went behind the scenes of the epic Oscar-winner to dig up 15 fascinating facts about its making.

1. IT’S ONLY PARTIALLY BASED ON UPTON SINCLAIR’S OIL!.

Though even the credits note that the film is based on Upton Sinclair’s Oil!, the novel served as more of a starting point for Paul Thomas Anderson, who adapted it for the screen.

“[W]ith There Will Be Blood, I didn't even really feel like I was adapting a book,” Anderson told The A.V. Club. “I was just desperate to find stuff to write. I can remember the way that my desk looked, with so many different scraps of paper and books about the oil industry in the early 20th century, mixed in with pieces of other scripts that I'd written. Everything was coming from so many different sources. But the book was a great stepping-stone. It was so cohesive, the way Upton Sinclair wrote about that period, and his experiences around the oil fields and these independent oilmen. That said, the book is so long that it's only the first couple hundred pages that we ended up using, because there is a certain point where he strays really far from what the original story is. We were really unfaithful to the book.”

2. PAUL THOMAS ANDERSON AND DANIEL DAY-LEWIS WERE FANS OF EACH OTHER’S WORK.

While producer JoAnne Sellar has said that There Would Be Blood may never have even happened if Daniel Day-Lewis had declined the role, Day-Lewis said that he was excited simply at the prospect of working with Anderson, as he was a fan of the director’s work.

“Initially, it’s all about the script,” Day-Lewis told IndieLondon. “But in [Anderson’s] case, I certainly knew his films and already admired him a great deal. And most particularly for his recent film Punch-Drunk Love. So even the very idea of working with him when the word came was something I was intrigued by. Nonetheless, had I read that script and not felt drawn into the world that he’d created, out of respect for him I’d have said: ‘Get somebody else, because I can’t help you here.’ But I was very drawn to the idea of working with him.”

3. DANIEL PLAINVIEW'S DARKNESS WAS PART OF WHAT ATTRACTED DAY-LEWIS TO THE CHARACTER.

Paramount Home Entertainment

Day-Lewis isn’t known for playing happy-go-lucky types and admitted that it was the darkness within the character of Daniel Plainview that further attracted him to the part.

“I daresay, because the unconscious plays such an important part in the work, the imagination being on the front line of that ... what could be more liberating than to explore with impunity the darker recesses of one's imagination and psyche?" Day-Lewis told NPR. "I suppose that has always appealed to me, and I always am most often intrigued by lives that seem very far removed from my own. [With] Plainview, [it] wasn't the violence of the man or the misanthrope of the man that attracted me particularly, but just that unknown life in its entirety."

4. ANDERSON FOUND INSPIRATION IN THE TREASURE OF THE SIERRA MADRE.

It’s been widely reported that Anderson watched John Huston’s The Treasure of the Sierra Madre every night before filming began on There Will Be Blood, but the director told Filmmaker Magazine that while the amount of times he watched the film before production “has gotten completely exaggerated,” he did find inspiration in the film.

“What was nice about that movie was that it's kind of a play wrapped up in the clothes of an adventure film,” Anderson said. “It's essentially a dialogue, a dynamic between these three guys. [The film's] traditional straightforward storytelling was what I was influenced by, and it was something that seemed to apply when trying to make a big story on a limited budget.”

5. DAY-LEWIS DID NOT BASE PLAINVIEW’S MANNERISMS ON JOHN HUSTON.

Another part of the There Will Be Blood/The Treasure of the Sierra Madre connection that seems to have been exaggerated is that Day-Lewis based the mannerisms of his character on John Huston, who wrote and directed the 1948 film and made a small cameo in it.

“A few people have asked me if I modeled [Daniel’s] voice on John Huston,” Day-Lewis told Time Out. “I didn’t. But I did listen to some tapes of Huston’s voice, among others. And there was something about the vigor of Huston’s language that appealed to me.”

6. DAY-LEWIS PUT A LOT OF THOUGHT INTO WHAT PLAINVIEW’S HAT SHOULD LOOK LIKE.

Paramount Home Entertainment

In an interview with The Washington Post, costume designer Mark Bridges explained that hats were extremely important to both the character of Daniel Plainview, and Day-Lewis for finding the character. “Leading up to the first time we see that hat, his hats kind of echo or inform what’s going on with his career and life,” Bridges said.

“Daniel Day-Lewis felt the hats were very important to his character,” Bridges continued. “There were three choices that were all good, and he took them and lived with them for days. He sort of creates mini worlds, and so he took them, just took them for a spin, so to speak, and settled on that one as what he felt most comfortable with and most represented in his mind the character he was creating. And it took on a kind of magic where he would be Daniel Day-Lewis, but you knew he was Daniel Plainview once the hat went on. So that was very rewarding to me.”

One more thing about that hat: “The sweat stains are real,” Bridges admitted. “It was worn day in and day out and has been much loved by all who’ve come in contact with it.”

7. PAUL AND ELI SUNDAY WEREN’T SUPPOSED TO BE TWINS.

In the film, Paul Dano plays twins Paul and Eli Sunday, but the brothers weren’t written as twins. Dano was originally cast in the smaller role of Paul Sunday, who visits Plainview to tell him about the oil under his family’s property in Little Boston, California. Another actor, Kel O'Neill, was cast as Eli and spent several weeks shooting before Anderson decided it just wasn’t working. As all of O’Neill’s scenes would need to be reshot, Anderson approached Dano about taking on the role—leaving him with just four days to prepare. (Dano received a BAFTA nomination for his work.)

Though rumors swirled that O’Neill departed the project because he was intimidated by Day-Lewis, all of the parties in question have gone on record to state that this was not the case.

“Filmmaking is so alchemical that sometimes certain factors don’t add up,” O’Neill told Vulture. “Some directors I’ve worked with—who very few people would say are better directors than Paul—just had a way of making me feel comfortable. For some reason, even though every other actor I know had a relationship with Paul that was super positive and where they did their best work, that just didn’t happen with me. I would attribute that primarily to a failure on my side: An actor should, with every ounce of their humanity, be attempting to give the director what he or she wants. And I recall going in and out on whether I could really do that.”

“It’s the only occasion in my life that, during the course of a piece of work, we had to re-cast and re-shoot stuff which I wouldn’t wish on anybody,” Day-Lewis told IndieLondon. “Paul [Dano] was already contracted to play the part of Paul, and we’d all considered him for Eli already, so it seemed like an obvious choice … He came out on a Friday evening and we were shooting scenes on Monday with him. And I swear to God on set that day he was a recognizable, fully formed character. I dare say he was slightly unsettled in himself, but you wouldn’t have guessed it. He was just right there.”

8. PAUL DANO DIDN’T ALWAYS KNOW WHAT TO EXPECT FROM DAY-LEWIS.

Miramax

When asked about what it was like to work opposite Day-Lewis in such an intense, antagonistic way, Dano told Collider that there were “definitely some moments where, you know, I was going, ‘Holy s**t.’ … Because we didn’t really rehearse and so sometimes, I didn’t know how big something that was going to come out of him was going to be, because he’s so powerful. And I don’t really want to say specific instances. I think you can probably imagine hearing some of the lines from that ending scene on the page but then, you know, the real deal is just a whole [other] level.”

9. DILLON FREASIER, WHO PLAYED HW, HAD NEVER ACTED BEFORE.

Anderson and his team had a bit of trouble casting the role of HW, Plainfield’s son. Though they looked at a number of professional child actors, Anderson realized that “we needed a boy from Texas who knew how to shoot shotguns and live in that world.”

So casting director Cassandra Kulukundis contacted a number of schools around Marfa, Texas, where they were shooting, and asked for their help. According to the Los Angeles Times, Kulukundis was asking for "a child who didn't play with GameBoys but worked outside," while Anderson described the ideal actor as "a man in a young boy's body."

One of the boys recommended to Kulukundis was Dillon Freasier, whom she met, did some improv with, and was impressed by. “[H]e just stayed in my mind, so I called [his mother] at home and asked if it was all right if I could come over that night," Kulukundis explained.

That same day, while heading to another school to meet with some additional kids, she got lost and was running late and driving at triple the speed limit. That’s when she got pulled over by a state trooper, who looked down at her license and said: "I think you're coming to my home tonight." The officer was Dillon’s mom, Regina. (Who let Kulukundis off with a warning.)

10. FREASIER’S MOM WAS NERVOUS ABOUT LETTING HER SON WORK WITH DAY-LEWIS.

While things clearly worked out well for Dillon Freasier, even after that little traffic stop incident, his mom wasn’t very familiar with Day-Lewis’s work. Before agreeing to let her son spend so much time with a man she knew nothing about, she decided to watch one of his films.

“Dillon’s mom thought she’d go and rent a movie with that fella Daniel Day-Lewis,” the three-time Oscar winner told The Mercury News. “So she went and got Gangs of New York and was absolutely appalled. She thought she was releasing her dear child into the hands of this monster. So there was a flurry of phone calls and someone sent her The Age of Innocence and apparently that did the trick.”

When Day-Lewis won a Best Actor Oscar for his work in There Will Be Blood, he thanked his young co-star in his speech. But Freasier missed it; he was already asleep.

11. THE FAKE OIL WAS MADE FROM THE SAME LIQUID MCDONALD’S USES IN ITS MILKSHAKES.

Miramax

When discussing the production design for the film with Entertainment Weekly, Anderson explained how they had to build an 80-foot oil derrick and fill it with fake oil. The recipe for that oil, according to Anderson, included “the stuff they put in chocolate milkshakes at McDonald’s.”

12. A PYROTECHNIC TEST PROVED PROBLEMATIC FOR THE COEN BROTHERS.

When awards season rolled around, There Will Be Blood and the Coen brothers’ No Country for Old Men went head-to-head for a number of the year’s biggest accolades. Oddly, the two films also ended up shooting in the remote and tiny town of Marfa, Texas at the same time. But Anderson ended up creating a bit of a problem for the Coens. While conducting a pyrotechnic test, Anderson and his team accidentally created a billow of smoke so large that it could be seen by the Coens’ cameras, leading them to have to cancel shooting for the day.

13. BEYOND READING, DAY-LEWIS DIDN’T DO MUCH PREP.

While Day-Lewis is known for going to some pretty far lengths to prepare for his roles, his prep for There Will Be Blood mainly consisted of reading. “I read the book [Oil!]. The first 150 pages or so introduce you to the world of the oilfields at that time, and there's a lot of great detail about the world of the drillers and the prospectors,” Day-Lewis told IndieLondon.

As for any special preparations he made to play such a devilish character, the actor admitted that he didn’t really have to do much. “I don’t know what that says about me, I wish I could say there was some monstrous … well, there are a couple of monstrous members of the family that I suppose I could have modeled him on, but in this case I didn’t. There was no model.”

14. NO, DAY-LEWIS DID NOT BUILD AN OIL RIG IN HIS BACKYARD.

Ever the Method actor, many outlets reported that to prepare for his role, Day-Lewis actually built his very own oil rig. Those stories were false. “It was rumored apparently that I’d built a derrick in a field behind my house in County Wicklow,” Day-Lewis told IndieLondon, “and I must say when I read that I thought: ‘That’s not a bad idea, I might try that!’ But we were a bit short on help at the time. Considering the way that I work very often, I do feel I’ve been soundly misrepresented so many times that there’s almost no point in even talking about it, but people tend to focus on the details of the preparation, the practical details in this clinic or that prison and so on and so forth … But for me as much as that work is a vital part of it and always fuel to one’s fascination, one’s curiosity, the principal work is always in the imagination. That’s where it’s going to happen if it’s going to happen anywhere at all.”

15. IT’S ANDERSON’S MOST PROFITABLE MOVIE.

Though Anderson’s latest film, Phantom Thread, is getting stellar reviews, There Will Be Blood remains the six-time Oscar nominee’s most profitable movie, with an estimated $40.2 million gross. It’s a far cry from the $26.4 million that his second most profitable movie, Boogie Nights, made.