Marvel's Doctor Strange is already a bona fide box office hit, earning $331.9 million worldwide thus far, after an impressive opening weekend of just over $85 million. Now that fans are flocking to theaters, director Scott Derrickson is revealing some new insight, including what character was his original choice for the primary villain. There will be SPOILERS below if you haven't seen Doctor Strange yet, so read on at your own risk.

Empire caught up with Doctor Strange director Scott Derrickson, who revealed that he originally wanted the Sorcerer Supreme to square off against Nightmare, the first villain he ever faced in the Marvel Comics. In the comics, Nightmare ruled over the dream dimension, reigning over all of the multiverse's bad dreams. Marvel Studios president Kevin Feige was the one who talked the director out of using Nightmare, which resulted in Dormammu being used instead. Here's what the director had to say below.

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"Kevin made a very cogent case. The trouble with starting with Nightmare is getting across the idea of the Dream Dimension as another dimension. The movie was challenging enough. It's already an exposition-heavy movie... Dormammu made the most sense. And he is the most present villain in the comics."

Other revelations made by Scott Derrickson is that the story takes place over one calendar year, with Benedict Cumberbatch's Stephen Strange spending approximately "three to six months" recovering from his vicious car wreck. The director also revealed that Benedict Cumberbatch actually had a dual role in the film, playing the Sorcerer Supreme, and providing the voice and facial capture for the devil Dormammu. Here's what Scott Derrickson had to say about why Benedict Cumberbatch pulled double-duty on the film.

"The reason for that was threefold. One, Benedict suggested it. [Two], the awesomeness of his voice - he was Smaug, of course. [Three,] he understood exactly who Dormammu was. He's the ultimate cosmic narcissist. There was something great about the mirrored relationship between the two of them."

Scott Derrickson added that Benedict Cumberbatch's voice was "blended slightly" with a different actor's voice for Dormammu, so fans wouldn't recognize it, adding that the Sorcerer Supreme is killed more than 1,000 times during the final confrontation. There was even a line with Strange says "We've been through this a thousand times. Literally." The director also added that the repetitive nature of this finale was a direct response to criticisms over previous MCU battles, where a city is destroyed.

"It was literally the play on that whole, 'oh, every Marvel movie ends with a city being destroyed during a fight, and then a portal that opens is closed just in time.' I said, 'well, dammit, we're going to un-destroy a city and we're gonna leave the portal open and Strange is going to go into it and we're going to see what's on the other side. That's how fresh my movie is, dammit!'"

By the end of the movie, Doctor Strange has become a powerful sorcerer, but he is not the Sorcerer Supreme. However, Scott Derrickson teased there were earlier versions of the script where Strange had actually become the Sorcerer Supreme at the end, but it was subsequently changed. Here's what the director had to say about why these changes were made.

"We had script versions where he became Sorcerer Supreme. We just had so many problems with that. It's premature. Once he's blown through to the New York sanctum, he's only accepted his role as a sorcerer in conflict for 24 hours. He's a long way from being Sorcerer Supreme. I think the comics took like ten years before he actually became the Sorcerer Supreme."

One of the main supporting characters is Chiwetel Ejiofor's Baron Mordo, who seemingly takes a villainous turn during the second post-credit sequence, where he takes another sorcerer's powers away. The director described Mordo as an unusual kind of a "fundamentalist.' Here's how the director describes this complex character below, and why he takes such a surprising turn in the post-credit sequence.

"He's a fundamentalist. Fundamentalism is such a pejorative word and immediately evokes images of angry extremism. In my experience, that's not usually what it looks like. I was a fundamentalist in high school. I went to a fundamentalist Christian high school and went to a fundamentalist church, and they were the greatest people, there was an amazing sense of community. The problem is when the messiness of real life enters and the inflexibility of a moral code cannot cope with the realities of moral relativism. When someone gives themselves over to an extraordinarily strict moral code, the process of breaking out of that is a violent one. He becomes disillusioned with the Ancient One's [moral contradictions]. The difference is Strange can accept that contradiction. Mordo cannot cope with it, and that's why the big jump at the [post-credits] tag makes total sense."

While Scott Derrickson is the only credited director, it seems the filmmaker got some help from other MCU filmmakers for two scenes. Thor: Ragnarok director Taika Waititi actually directed the first post-credits scene, which features Thor (Chris Hemsworth) meeting with Doctor Strange, while Guardians of the Galaxy 2 director James Gunn shot the Stan Lee cameo. James Gunn had previously revealed that he had shot four Stan Lee cameos in Atlanta, which Scott Derrickson confirmed below.

"We all shoot each other's movies! James Gunn shot four Stan Lee cameos for four different movies in Atlanta. He was texting me pictures of the frame."

Scott Derrickson also confirmed that the Staff Of One, a powerful object from the comics that is wielded by Tina Minoru, is shown in the Hong Kong sanctum, but Tina is not wielding it in that scene. The director also revealed that he wanted to use Jimi Hendrix's "Are You Experienced?" to play over the end credits, but that didn't happen because of the guitarist's family. The second choice was Pink Floyd's Interstellar Overdrive, used during the car crash scene, but that was too expensive. Here's what Scott Derrickson had to say about what was almost used as the end credit music, before composer Michael Giacchino came up with the track "The Master of the Mystic."

"At first I wanted Jimi Hendrix's Are You Experienced? but the Hendrix family demanded to see the whole film ahead of time, and they're very expensive. We didn't have time to do it. They (Pink Floyd) wanted like $500,000 just to play over the end credits, and we weren't going to do that. So Giacchino came up with that."

While Michael Giacchino was recording that song, at Abbey Road Studios, Scott Derrickson revealed that Paul McCartney himself stopped by. The legendary recording artist told the composer "shades of Walrus," referring to The Beatles classic song "I Am the Walrus." The director revealed that he actually thought he had dreamed that moment the next day. Hopefully we'll learn more about Doctor Strange as it continues its theatrical run.