[Source: Reuters]

A young Sylvester Stallone had one non-negotiable demand when he was ‌trying to sell his script about a small-time boxer named Rocky Balboa.

Stallone wrote the lead part for himself. “I play Rocky,” the then-unknown actor insisted when studio executives suggested a Hollywood star such as Ryan O’Neal for the title role.

The behind-the-scenes fight ​to get “Rocky” to the screen is the subject of “I Play Rocky,” a new film that ​Amazon MGM Studios (AMZN.O), opens new tab is releasing in theaters on Friday.

In many ways, the battle to ⁠make the 1976 big-screen hit “Rocky” mimics the plot of the movie itself. It tells the story of ​an underdog who refuses to give up on his dreams.

Anthony Ippolito plays Stallone, starting from a time when ​the future megastar was a struggling, homeless actor looking for work in New York City.

To prepare for the role, Ippolito searched for footage of Stallone at the time and found little outside of appearances on the TV show “Kojak” and in the ​low-budget film “The Lords of Flatbush.”

“It was hard to find because he wasn’t the star that he came to ​be,” Ippolito said.

Married with a pregnant wife, Stallone refuses life-changing amounts of money to sell the “Rocky” script and let another ‌actor ⁠take the lead role.

When he finally gets his wish to star in the film, he and the filmmakers face a tight budget and unexpected production challenges.

Ippolito’s performance worked because he did not try to merely imitate Stallone, who is known for his distinctive deep voice and slurred speech caused by a birth defect, “I ​Play Rocky” director Peter Farrelly ​said.

“This guy embodied him,” ⁠said Farrelly, director of the Oscar-winning film “Green Book.” “He became Rocky, and he understood the difference between” Stallone and his character.

The real-life Stallone was not involved in ​the production, but he did give his blessing to the script and to ​the casting of ⁠Ippolito.