Sylvester Stallone was a struggling 30-year-old actor with just US$100 in his bank account when he wrote a screenplay about a boxer named Rocky.
Yet, when a studio offered to buy the script for US$250,000 so that Ryan O'Neal, Burt Reynolds or another big name could star in it instead of him, he refused.
Instead, he took less money so he could play the underdog fighter himself in the 1976 film, which went on to become a huge hit, winning three Oscars, including the Best Picture award along with Best Actor and Best Screenplay nominations for Stallone himself.
It would also lead to five sequels, more than US$1 billion in tickets sold and, now, four decades later, a seventh film that reboots the franchise with actor Michael B. Jordan as a young boxer Rocky takes under his wing.
Opening in Singapore tomorrow, Creed is helmed by 29-year-old writer-director Ryan Coogler, whose doggedness reminded Stallone of himself.
Speaking to Life and other press in Philadelphia, where the movie is set, the star says the young film-maker's persistence in convincing him to revive his Rocky character, which he had been reluctant to do, showed him that they shared that "stubborn gene".
This was the trait that had underpinned his own fateful decision to insist on playing Rocky in the first movie - that and the fact that he had by then "mastered the art of poverty".
"I was looking at my dog as a meal,'' quips Stallone, who then became one of Hollywood's biggest action stars, appearing in the Rambo (1982-2008) and The Expendables (2010-2014) films, many of which he also co-wrote and directed.
"No, seriously, just to make it in this business, you have to have the stubborn gene and when you don't adhere to that and you give in, you're going to regret it.
"Like when Ryan came in to see me. He may look nice, but he's very stubborn and wilful."
Wilfulness helps during those "moments in your life when you hit a major crossroads and this is going to determine your future or your life", says Stallone, 69.
In 1976, he also knew the pain of giving up US$250,000 would fade, whereas "the scar and self-loathing of watching O'Neal play Rocky" would not.
Coogler, too, was struggling to make his name in Hollywood when he first pitched his idea for a new Rocky film revolving around Adonis Creed, the son of Apollo Creed - a boxer Balboa fights and then becomes friends with in the earlier films.
At that point, Coogler had not yet completed the critically acclaimed Fruitvale Station (2013), a powerful indictment of police brutality and racial profiling that he wrote and directed based on the true story of a young black man killed by police in Oakland, California.
Stallone confesses that his initial reaction to the idea of making another Rocky film was: "Um, no. No, no, no.
"Because it was such a struggle to get the last one, Rocky Balboa (2006), done and I was so happy with the conclusion of the Rocky story that I thought we needn't go any further with it and I dismissed his idea.
"But Ryan was very, very adamant about doing it, and he came back a year and a half later. And then I thought, 'My story is told, but there's a whole other story and two generations out there since Rocky started. Their story has not been told and (the idea for Creed) is very ingenious, so I finally agreed to do it.'"
Coogler - who is relatively inexperienced to be handed a big franchise such as this, even though Fruitvale Station earned more than US$17 million against its budget of US$900,000 - remembers his first meeting with Stallone.
The encounter did not go smoothly, says the director, who was starstruck at meeting the man he had grown up watching in the boxing films he and his father had bonded over.
"We were due to start filming Fruitvale Station in a week and I was losing my mind feeling completely overwhelmed when I got a call from my agent, who said: 'Buy a plane ticket, Sly's got an hour tomorrow and wants to see you.'
"So I rushed over to Sly's office in Beverly Hills and when I met him, it was like nothing I imagined - I imagined meeting Rocky - and I have to tell you I was shocked at how different he is from that character.
"Then I realised, 'Holy smokes, that was a performance, all that stuff (he did in the films) was acting choices and this dude is phenomenally talented.'
"But the whole time I'm talking and pitching this story to him, I could tell he was thinking, 'This kid, I don't know what he's talking about.' He was dying to get out of there."
Stallone eventually came around to the idea of a story where his character would act as a mentor and father figure to Creed, who, in turn, would help the older man through a difficult time of his own.
Stallone - who has three teenage daughters with wife Jennifer Flavin, 47, and a 46-year-old son from a previous marriage - embraced the idea of taking a backseat to a younger hero.
"That's why I think it's just so phenomenal - we can reach generations that weren't even around when we did the third Rocky movie (1982's Rocky III), forget about the first one," he says.
Referring to Coogler and Creed co-writer Aaron Covington, he adds: "What these guys can do that I can't do anymore is they're living in the here and now and I pretty much live in the past because that's where I acquired all my knowledge."
In a separate interview, Coogler tells Life he is conscious of the fact that this iconic franchise is being relaunched with a young black man as the central character.
"The character of Apollo Creed was already in the franchise and popular with fans, (but) he was just a supporting character.
"And film-making for me has always been about that - I came to it with a real curiosity for characters and people whose stories aren't the main focus. It's probably because I'm African American myself, so, oftentimes, the characters that looked like me didn't get the full focus. So it's always a pleasure for me to tell stories that give them that focus and, through that focus, highlight things that you might not have seen about the main character."
Stallone is still marvelling at the films' longevity.
"What's amazing is this character and the stories have stayed around without any special effects, without any car chases, without blowing anything up, which is what I usually do. No bullets, no cursing, no sex scenes, nothing.
"I'm very proud and stunned. And (Creed) is another beginning - hopefully, we'll have a whole new series and it will just continue to go on."
•Creed opens in Singapore tomorrow.