When he was a young boy, Garth Jennings made a film emulating “First Blood,” a 1982 action flick that was the first in the Rambo series. Yet Jennings and producer Nick Goldsmith insist their childhoods were not the basis for the characters in their new film, “Son of Rambow.”

Two young boys, one seemingly obedient and religious, the other, the class troublemaker, form an unlikely friendship and bond over the production of a homemade film of an adventure story inspired by one of the character’s first exposure to television via “First Blood.”

Goldsmith and Jennings’ first draft was based on their childhood, but it had a fatal flaw.

“The script was a bit dull,” Goldsmith said. There was no conflict. Their childhoods were just too happy.

And there was another problem.

“We never started with a plot,” he said. “We wrote it with a feeling.”

Goldsmith and Jennings said they wanted to capture how it felt to be an 11- or 12-year-old boy. They both admitted it was not the best angle from which to attack script-writing.

“We wrote at least four completely different films,” Goldsmith said, with multiple drafts of each, including a Goonies-like script and a slice-of-life film, before getting the script that would eventually make “Son of Rambow.”

William Proudfoot (Bill Milner), a quiet boy who seemingly follows the orders of his mother and their strict religious sect, has an active imagination full of dragons and monsters, colorfully illustrating his Bible, his school workbooks and the inside of a bathroom stall at school. Because of his religion, he isn’t allowed to watch television, and has never seen a movie of any sort. A chance encounter with troublemaker Lee Carter (Will Poulter) forms an unlikely friendship between the two boys.

At Carter’s house, Proudfoot first sees a pirated version of “First Blood.” Suddenly, his world is turned upside down. He has a new role model and he passionately embraces the role of Rambo’s son, out to rescue his father from the clutches of an evil scarecrow and flying dog.

Lee Carter scams Will into helping him make a film for a BBC film contest, “Screen Test.” The film eventually takes on the story from Will’s imagination. Their lives are further complicated with the inclusion of a too-cool French exchange student and his entourage.

Inspired by “Screen Test,” a real competition back in the ’80s, Goldsmith and Jennings will be the judge of their own homemade film contest. Jennings’ film inspired by “First Blood” can be found on the contest’s Web site, and will be put on the U.S. and U.K. release of the DVD, alongside the film by the contest winner.

Because “Son of Rambow” stars kids and talks about their imaginations and relationships, it’s an unusual subject to tackle and still keep an adult audience interested. That made the script a hard sell to potential financers, who kept asking, “Who is this for? How do we market it?”

“They just didn’t get it,” he said. Goldsmith was confused. He tried to explain this film would appeal to a universal audience. Isn’t a film for everyone the “Holy Grail” of movies, he wondered?

As a result of the financing difficulties, the multiple versions of the scripts, and the interruption of another film the two worked on, “The Hitchhiker’s Guide to the Universe,” “Son of Rambow” has been more than eight years in the making. Back then, another Rambo film seemed implausible, and it’s dumb luck that the release of their film coincides roughly with the fourth in the Rambo series, released 20 years after “Rambo III.” While schedule conflicts prevented Jennings and Goldsmith from actually meeting Sylvester Stallone, Stallone saw the film and really liked it, according to Goldsmith and Jennings.

They, too, are satisfied, and they give much of the credit to the child actors, most of whom were new to film, and even new to acting.

“It’s come out better than we hoped,” Jennings said. “Because of the kids – they were the extra magical bit for me.”