5 Revelations from Sylvester Stallone’s Netflix Doc Sly: From a Violent Childhood to His Jealous Dad

Sylvester Stallone makes some surprising revelations about his past in his new Netflix documentary, Sly. 

In the doc’s candid interviews, the 77-year-old filmmaker and screen icon delves deep into his difficult childhood in New York City and Maryland, plus his lifelong fascinations and Hollywood career aspirations — which changed practically overnight with the 1976 release of Rocky .

“Do I have regrets? Hell yeah, I have regrets!” exclaims Stallone in the film’s opening moments. The Rambo and Expendables star reflects on several of his most well-known acting and writing projects, even picking apart why some didn’t work critically or commercially as well as others.

Also featured in the Thom Zimny-directed film are interviews with friends and costars, including Arnold Schwarzenegger, Henry Winkler and Talia Shire, plus critics and movie buffs like Quentin Tarantino. 

Read on for the biggest bombshells and previously untold stories about Stallone. Following its premiere at the 2023 Toronto International Film Festival, Sly is now available to stream on Netflix. 

Stallone’s “snarl” came from almost being born on a bus

Stallone has previously explained that his crooked smile and slurred speech — which became two of his signature traits as he became a Hollywood screen icon — is partial facial paralysis from nerve damage at birth. 

In Sly, Stallone remembers his mother, Jackie (who died in 2011), and tells the story of how that difficult birth began. “Even though she was nine months pregnant, she kept riding around on the bus. And she [went] into labor.”

He continues, “Somebody was smart enough to get her off the bus, they carried her into a charity ward. And that’s where I was brought into the world via this accident which kind of paralyzed all the nerves on the side of my mouth. So I was born with this snarl.” 

His father Frank Stallone Sr. inspired some of his movie characters

“My father was Rambo, in reality” Stallone reveals in the documentary. Machine-gun-toting Vietnam War veteran John Rambo, who first appeared on the big screen in the 1982 hit First Blood, was one of many characters inspired by the filmmaker’s actual life. 

“I was raised by a very physical father,” says Stallone, recalling physical and verbal abuse from his childhood. The way Frank Stallone Sr. would hold his utensils while eating dinner, he explains, predicted violence to come. “Nothing was ever settled verbally. It was usually a physical ultimatum.”

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Sly makes clear that quiet menace and physicality is what informed Stallone’s conception of the John Rambo character. Holding up a photo of his blankly stoic father, who died in 2011, he says, “You do not want to mess with this guy.” 

Elsewhere, the doc intercuts footage of Stallone discussing his father with the scene in Rocky in which trainer Mickey (played by Burgess Meredith) offers to coach Rocky Balboa, who at first refuses before relenting, accepting him as a father figure. 

Stallone and his brother say they grew up “no stranger to serious pain” with their parents

“I was no stranger to serious pain,” says the Cliffhanger star of his upbringing. The toughness required, he explains throughout Sly, ended up informing his philosophy: “I think it just became, ‘I’m not gonna break.’”

His “physical” father, according to Stallone, once grabbed his 13-year-old son off a horse midway through a polo match. 

But according to brother Frank Stallone Jr., Jackie was just as comfortable keeping the two boys in line. “Our mother was pretty bad too,” he says in the film. “She was pretty handy with the old hairbrush… she had these long nails that would never break.” 

Frank Stallone Sr. was jealous of his son’s success 

Sly includes interviews from filmmaker John Herzfeld, whose collaborations with Stallone date back to the low-budget self-produced silent film they created in 1969. The writer-actor-director recalls shooting that Western-inspired movie with Frank Stallone Sr., who in his memory enjoyed “a little too much” playing a character who shoots and kills Stallone's character. 

It was after the box office-dominating and Oscar-winning success of Rocky, says Herzfeld, that Frank Stallone Sr. reached out to him with a script about “the real Rocky.” 

When Herzfeld objected, suggesting Stallone had already made a boxing movie and should be the one to check out the script, Stallone’s father refused to do so. “He was still competing with Sly,” explains Herzfeld.

That jealousy extended beyond his son’s Hollywood success; when Stallone began playing in nationally ranked polo matches by age 13, brother Frank Stallone Jr. says, “My father wasn’t liking that so much.”

He adds that Stallone could have played the sport at the highest level “if it wasn’t for my father browbeating him. And that’s why he quit polo.”

Stallone opens up about his son Sage’s death and their relationship

A somber sequence in Sly shows footage of Sage Stallone, who before dying at age 36 due to coronary artery disease, made his feature film debut with his father in 1990’s Rocky V.

Herzfeld says that Stallone wrote the film with Sage in mind for the part of Rocky's son. “He wanted to give him this opportunity that was so hard for Sly to get.”

When asked whether he drew from personal experience in crafting the story's difficult father-son relationship, Stallone answers, “Unfortunately, yes.”

He continues: “I try to take something that actually is what I wish I had done in real life, but I wasn’t able to do that in reality. And so quite often I would do it theatrically, magically… A lot of that is true. Unfortunately, you put things before your family. And the repercussions are quite radical and devastating.” 

Along with that present-day footage, the documentary plays footage from a Rocky V premiere. Standing with his son on the red carpet, Stallone says, “There’s a line in the movie, ‘I’m so glad he’s born because now I can live through your eyes.’ That, I think, is what fathers look to their children for. It’s an extension of, a slice of immortality. As long as he’s alive, your memory will always be alive, that you did something right. I mean, you hope for that.” 

Sly is now streaming on Netflix.