Sylvester Stallone was a struggling actor pushing 30 and working odd jobs in Los Angeles when he wrote the screenplay for "Rocky" during a three-and-a-half day stretch in early 1975. He had one non-negotiable condition when he pitched the script to producers at United Artists: only he could play underdog Philly pugilist Rocky Balboa.

"I Play Rocky," an upcoming biopic that tells the story behind Stallone's Oscar-winning film, unveiled its first trailer this week ahead of its theatrical release on Nov. 6. The movie, directed by Peter Farrelly ("Green Book," "Dumb and Dumber"), stars Anthony Ippolito as Stallone fighting for his breakout role.

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The trailer shows Ippolito as a young Stallone preparing his script and holding firm with producers on his demand to be the star actor. It also features re-creations of some of the film's most memorable scenes, including Balboa throwing punches at a hanging side of beef.

Stallone's résumé included only a handful of bit roles in movies in the early 1970s, including the softcore pornographic flick "The Party at Kitty and Stud's." The inspiration for "Rocky" came from Stallone's viewing of a 1975 bout between Muhammad Ali and Chuck Wepner, a liquor salesman who faced the heavyweight champ as an obvious underdog. Stallone was blown away by Wepner's grit in the match, which went 15 rounds and included an unexpected knockdown of Ali. Wepner's loss gave Stallone the premise for a movie about a scrappy, Italian American from Philly stepping into the ring.

Stallone initially got the script in front of ABC executives with help from "Happy Days" star Henry Winkler. The network ended up buying the script, but wanted to replace Stallone as the writer and make significant changes. Winkler begged ABC to sell it back to Stallone, giving him a chance to shop the script to other studios and pitch himself as the star.

When Stallone ran the script by United Artists producers Irwin Winkler and Robert Chartoff, they loved the concept but wanted an established actor to play Rocky Balboa. Burt Reynolds, Robert Redford, James Caan, Nick Nolte and Ryan O'Neal were among the names floated for the role. Stallone refused to part with the script unless he could play Rocky, turning down a maximum offer of $360,000 before the studio relented and gave him a chance.

With a production budget under $1 million and a grueling schedule, "Rocky" was primarily filmed on location in Philadelphia during a 28-day stretch in January and February of 1976. In one interview, Stallone recalled initially planning to run up the Philadelphia Museum of Art steps with Rocky's loyal bull mastiff Butkus. He also described how the film's famous meat locker scene left his hand mangled from punching a frozen carcass. 

"Rocky" got a limited release in November 1976 before it was distributed widely in U.S. theaters that December. The film quickly built momentum by word of mouth, garnering critical acclaim on the way to grossing an estimated $225 million at the international box office. The movie was nominated for 10 Academy Awards, earning Oscars for best picture, best director and best film editing. Stallone, nominated for best actor and best original screenplay, didn't take home any awards. But the film turned him into an overnight Hollywood star, spawning an enduring franchise and cementing his reputation as a rugged, self-made writer and actor.

Fifty years later, "Rocky" is immortalized in Philadelphia lore with its own festival and a bronze Balboa statue (one of a few made by sculptor Thomas Schomberg) that serves as a global pilgrimage site for fans of the franchise. 

Ippolito, best known for playing Al Pacino in the Paramount+ miniseries "The Offer," recently said he studied Stallone's role in the 1974 coming of age film "Lord of the Flatbush" to get a sense of the actor's style and mannerisms before "Rocky." Stallone played a teenager in a Brooklyn gang. Ippolito also watched old interviews with Stallone.

"I had to put on some weight because he was a pretty muscular dude and I was a little slimmer," Ippolito said during a Fandango interview with the "I Play Rocky" cast. "... I just tried to immerse myself in the filmography as much as I could."

The cast for "I Play Rocky" features Matt Dillon as Stallone's father, AnnaSophia Robb as Stallone's first wife, Sasha Czack, and Kiki Seto as Rocky's fictional love interest Adrian Pennino.

Stallone, 80, was not directly involved in the making of the biopic but offered advice to Ippolito.

"I got to Zoom with him briefly, but he could not have been more gracious and more generous about sharing what that experience was for him," Ippolito said. "He really did have a lot of things working against him and not too many people in his corner at the time, other than a few."