After producers Irwin Winkler and Robert Chartoff became interested in the script, they offered Sylvester Stallone an unprecedented $350,000 for the rights. He had $106 in the bank and no car, and was trying to sell his dog because he couldn't afford to feed him, but he refused to sell unless they agreed to allow him to star in the film. They agreed, on the condition that Stallone continue to work as a writer without a fee, and that he work as an actor for scale. After Winkler and Chartoff purchased the film, they took it to United Artists, who envisioned a budget of $2 million with an established star, particularly Robert Redford, Ryan O'Neal, Burt Reynolds, Nick Nolte or James Caan. When Winkler and Chartoff told United Artists that they could only get the screenplay if Stallone starred, United Artists cut the budget to $1 million and had Chartoff and Winkler sign agreements that they would be personally liable if the film went over budget. The final cost was $1.1 million. Chartoff and Winkler mortgaged their houses for the last $100,000.
After the end of filming, Sylvester Stallone kept the two turtles "Cuff" and "Link", and as of June 2019 he still had them, alive and well. The same turtles also appeared on Rocky Balboa (2006).
Most of the scenes of Rocky jogging through Philadelphia were shot guerrilla-style, with no permits, no equipment, and no extras. The shot where he runs past the moored boat for example, the crew were simply driving by the docks, and John G. Avildsen saw the boat, and thought it would make a good visual, so he had Sylvester Stallone simply get out of the van and run along the quays, while Avildsen himself filmed from the side door. A similar story concerns the famous shot of Rocky jogging through the food market. As he runs, the stall keepers and the people on the sidewalks can clearly be seen looking at him in bemusement. While this works in the context of the film to suggest they're looking at Rocky, in reality, they had no idea why this man was running up and down the road being filmed from a van. During this scene, the famous shot where the stall owner throws Rocky an orange was completely improvised by the stall owner, who had no idea that a movie was being filmed and that he would be in it.
The ice rink scene was originally written to feature 300 extras, but the production couldn't afford so many people. When Sylvester Stallone turned up to shoot the scene, to his horror, there was only one extra. So, Stallone hastily threw together the scene as it exists in the completed film. This scene has become one of the most popular in the entire Rocky saga.
Frank Stallone: the lead singer of the street band, and "The Bum from the Dark" who passes Rocky and Adrian on the way home from their date.