According to his biography, the thing that made John Romulus Brinkley famous wasn’t even his idea. In The Life of a Man, Clement Wood writes that in 1917, Brinkley, a doctor running a drug store in Milford, Kansas, was talking to a farmer struggling with impotence when he jokingly referenced goats going at it nearby. “You wouldn’t have any trouble, if you had a pair of those buck glands in you,” he said.

“Well,” replied the farmer, “why don’t you put ‘em in? Why don’t you go ahead and put a pair of goat glands in me? Transplant ‘em, graft ‘em on, the way I’d graft a Pound Sweet on an apple stray.”

Brinkley balked at first, but eventually—after arguing with the farmer about it until 3 a.m.—he was persuaded to perform the surgery, for which he was paid $150. Within the next few months, he performed the operation several more times. Each time, according to The Life of a Man, the surgery worked. Impotence was cured. Babies were being conceived.

By today's standards, of course, we know that this is pure bunk—Brinkley was clearly a quack. His xenotransplantation surgery could never have worked. But in the early 20th century, this fact was not so clear, and Brinkley’s renown—and his fortune—grew. Soon, the doctor was charging $750 per surgery, performing them by the thousands, and working with celebrity clientele. He was even mocked, on film, by Buster Keaton. Brinkley and his wife, Minnie, and their son, nicknamed Johnny Boy, lived like kings, first in Milford, then in Del Rio, Texas. During the Great Depression, while much of the nation struggled, Brinkley sold other cures at a rate of $100 a treatment, raking in $1 million a year.

As unbelievable as it may sound, a goat testicle–based cure for impotence was just the beginning for Brinkley. He was an early adopter of radio, pioneered the advertorial, and conducted a write-in campaign for the governorship of Kansas. And, of course, he had his fair share of enemies, including the Federal Radio Commission and the American Medical Association. But it was his own hubris, not his enemies, that would eventually bring Brinkley down.

When she first read about Brinkley in Pope Brock’s biography of the doctor, Charlatan, documentary director Penny Lane (Our Nixon) knew she had to turn the doctor’s incredible (and ultimately tragic) story into a movie. “I just immediately was taken by the story,” Lane tells mental_floss. “It seemed ready-made for a film.” Lane’s documentary about Brinkley, Nuts!, premieres at this year’s Sundance Film Festival.

Once she had decided to make a documentary about Brinkley’s life, Lane dove right into archival research. Using Brock’s sources in Charlatan as a starting point, “I just started flying around the country and going to these small county historical societies,” she says. “I actually found a number of just private individuals who were interested in John Brinkley and had their own personal collections that they’d collected on eBay over the years—photographs, his advertisements, brochures, and home movies.” Trial transcripts and contemporary newspaper articles also served as important sources.

Lane spent two years traveling to collect archival materials. One key piece she found was The Life of a Man. Wood, she says, “was a hack—he would write whatever you paid him to write.” Brinkley paid Wood to write The Life of a Man, then published it at his own publishing house in the 1930s; he gave copies away as promotional items. “The book is so crazy—it’s full of the most insane purple prose you’ve ever read,” Lane says. “It’s just over the top: Comparing Brinkley to Jesus, and Galileo. I was so taken with the tone of it—it just cracked me up.”

The book provided an artistic breakthrough: Lane knew she wanted it to be the center of her documentary. “It’s kind of the inspiration, because the book cloaks itself in a kind of authority,” she says. “It’s a biography, and you’re like, ‘OK, I know what biographies are. They do a bunch of research and they tell the truth.’ But it’s not a biography. It’s full of lies. The writer had no compunction about just making stuff up. I loved that! I was amazed at how you could look at something and think you know what it is, and not realize that you’re just being duped.” Parts of The Life of a Man are used as narration throughout Nuts!.

Other important archival finds included Brinkley’s home movies and transcription discs Brinkley had recorded. “I was lucky,” says Lane, because “it wasn’t common for radio operators to do that at the time.” (The discs were actually pre-recorded radio spots that Brinkley had created to get around Federal Radio Commission laws.) Still, she couldn’t use much of those discs: Brinkley’s recordings “must’ve been considered really seductive and convincing in the 1930s,” she says, “but if you listened to him on the radio now you’d be like, ‘This is not seductive and convincing. This is actually just creepy and weird.’ So I didn’t get to use very much of his radio stuff.”

Her best find was a 1922 film Brinkley had created called Rejuvenation Through Gland Transplantation. “It looks like a science film—it’s got illustrations of the human testicle, and it shows how the procedure works, and photos of some of the people that ended up having this procedure,” Lane says. “Of course it’s not a science film, it’s an ad they made to look like a science film, which is perfect.” The film was discovered, by chance, at the Library of Congress, where it was mislabeled. “No one really knows where it came from,” Lane says. “It really gave me the kind of material that you’d want for a film like this—you want to be able to show the cross section of the testicle and how it works. It was totally a score.”

With her materials assembled, Lane began to piece her documentary together—but because of how she wanted to approach it, she found herself in somewhat unfamiliar territory. “I had this risky idea, at the beginning, that I wanted to create this film in a way where I’m creating the maximum possible chance that a viewer could fall for Brinkley’s bullshit,” she says. “I wanted to be manipulative, and then I wanted to, obviously, unravel that in the film. But I thought, ‘Well, can I do that? Is it really possible to pull that off?’”

She had plenty of archival material to work with, though not as much as she'd had in her previous documentary, Our Nixon (which mental_floss discussed with the director at SXSW in 2013). “With Nixon, I had almost 4000 hours of candid audio tape, and it really made it possible for me to construct actual characters,” she says. “With Brinkley, I had enough stuff to do a film that was chock full of awesome archival material of all kinds, but I didn't have any candid audio, so it was much harder to figure out how to make him a character.”

What she needed, Lane realized, was a script—not something a documentarian normally has to think about. “For Brinkley to be seductive and feel real, I needed to script him and create scenes from his life,” she says. So she brought in writer Thom Stylinski, who helped to craft the narration and penned reenactment scenes that were later animated. “I’m not sure I would’ve had the confidence even to do it without him,” she says. “I was like, ‘How do you write a script? I don’t even know.’ It was just really outside the realm of what I had done before.” The animation for each chapter of Brinkley's life was created by a different company and was partially funded on Kickstarter.

It took eight years for Lane to craft Nuts!, which follows Brinkley’s life from his humble beginnings in Milford to the openings of Brinkley hospitals in several states and the creation of “Formula 1020,” which Brinkley claimed was a distillation of goat glands that would cure everything from impotence to insanity. Lane says the most fascinating and outrageous thing about Brinkley was his ability to stay one step ahead of the people who wanted to bring him down. “It was this fun cat and mouse game,” she says. “Watch people try to stop him, and then watch him outsmart them, over and over again. Con men—we just love those characters. Even if you know they’re the bad guy, it’s really fun to watch the one who just keeps winning ... You can’t help it. It’s very appealing.”

The prime example was when authorities shut down Brinkley’s powerful and popular 5000-watt Kansas radio tower. “He was like, ‘Well, no problem. I’m going to go to Mexico, and I’m going to build a new radio station. It’s not going to be 5000 watts, it’s going to be a million watts, and you’re really going to regret ever having shut down my radio station in Kansas,’” Lane says. “I think that was the most amazing move of his entire career. It was brilliant.”

But it all came tumbling down when Brinkley sued the American Medical Association’s Morris Fishbein for libel in 1939. (In “Modern Medical Charlatans,” a two-part article published in Hygeia, a magazine from the American Medical Association, Fishbein had written, among other things, that “In John R. Brinkley, quackery reaches its apotheosis.”) Once Brinkley was in court and on the stand, he was exposed as a fraud—he wasn’t even a real doctor (he had received his degree from a diploma mill).

In short order, Brinkley was sued by former patients for malpractice and investigated by the IRS for tax fraud. By 1941, he had declared bankruptcy. Soon after that, he was investigated for mail fraud. He died of heart failure in 1942, leaving his wife (who supported his claims that the goat gland surgery was legit until she died) and his son penniless.

“It’s a really tragic story—ultimately, a very American tragedy: These complicated characters who are geniuses, who are born with nothing, on the outskirts of society, apply themselves and become very successful and famous, and then go down really badly, in a way because of their own hubris," Lane says. "If he hadn’t sued the AMA for libel, Brinkley probably could’ve just kept going—but he actually dragged himself into court, and that’s what destroyed his credibility and his career.”

Still, despite his misdeeds, it’s hard not to feel bad for Brinkley. “He’s not just the stock villain—I think he’s an interesting, real human being,” Lane says. “But at the end of the day, it’s just irrefutable that he was a con man. A lot of people love him because he did a lot of charity, and that's great. But it doesn’t take away from the fact that he was a con man.”

Nuts! premieres at Sundance tonight. Click here to find out when and where it’s playing at the festival.

All images courtesy of Nuts!.