On Oct. 21, Universal Home Entertainment will host a red-carpet screening at Lincoln Center of “Back to the Future,” wrapping a week-long celebration tied to the day shown on Marty McFly’s time-machine DeLorean car. It’s a pretty impressive array of activities, considering the movie started out with nobody wanting to make it.

Bob Gale, who scripted the 1985 original with Robert Zemeckis, told Variety this week that they spent years trying to get it made, but most studios thought it was too tame, saying “very nice, very sweet, but take it to Disney.” However, when they finally met with Disney, execs thought it was too racy, nervous about Lorraine’s attraction to Marty McFly (who’s her son, though she doesn’t know it because he’s visiting from the future).

The reason he sets the DeLorean to Oct. 21, 2015? It’s the day 30 years in the future when the Cubs are predicted to win the World Series. Gale told Variety that he tried to figure out when the final game of the Series would have played: “I did my homework as a baseball fan.”

Steven Spielberg always supported the project. Gale and Zemeckis had written Spielberg’s “1941” and followed that with “I Wanna Hold Your Hand” (1978) and “Used Cars” (1979). None was a hit, so “Back to the Future” was a tough sell. But after Zemeckis directed the successful “Romancing the Stone,” the duo revived the “Future” idea; they returned to Spielberg’s Amblin Prods. and it became the pet project of Sid Sheinberg, president-CEO of MCA Inc.

Spielberg was “very active” as producer of the Universal film, but gave them leeway because he has a “filmmaker first” policy, Zemeckis told Variety on June 24, 1985, just before “Future” debuted. That 1985 article by James Greenberg chronicled all the production woes. Five weeks into the shoot, they assembled footage and found Eric Stoltz “was not the character that the filmmakers envisioned.” He was fired and replaced with Michael J. Fox.

It’s always tough to replace a lead actor, but it almost never happens so far into production. The production team had to shoot around Fox’s “Family Ties” TV schedule. Fortunately, some of the footage was still usable and the 1955 town built on the Universal lot had not been converted to 1985. “The biggest challenge of the film was to shoot all out of sequence because of Fox’s schedule, work nights and make it all look seamless,” the 1985 story reported. Some scenes were shot without Fox present.

As the final challenge, the filmmakers and two editors went into overdrive when Sheinberg requested the film be ready for July 3, rather than original July 19 target date.

“It will be interesting to see if kids are too rebellious today to go to a movie that their parents like,” Zemeckis said at the time. It turns out that wasn’t a problem. The film spawned two sequels and multiple generations of fans.

Admirers include Chris Martin of Coldplay and Seth MacFarlane; John Mayer said he became a musician because of the scene in the film when Fox takes the stage to perform “Johnny B. Goode.”

Gale said the film and its two sequels have lasting appeal because of the central premise. “Every human goes through a moment when they suddenly understand the concept that their parents once were children themselves. For a kid, that’s cosmic: ‘These grown-ups who know everything were once young screw-ups like me!’ When Marty travels to the past, he discovers the answer to the question ‘What would it be like to be on my parents’ first date?’ ”

New York celebrations included a pair of concerts at Radio City Music Hall last week, with Alan Silvestri conducting his score for the trilogy, and with 20 minutes of added music. On Oct. 20, Universal Pictures Home Entertainment launches a 30th anniversary trilogy on Blu-ray and DVD. That same day, HarperCollins releases the book “Back to the Future: The Ultimate Visual History,” with photos, memos and unreleased material.

The next day, there is the first issue of a “BTTF” comic book, explaining how Marty and Doc met. That evening, there is the Lincoln Center screening, and 1700 theaters will host screenings of the films, with each venue deciding if it wants to show all three films or some combo.

And during the month of October, Amazon Prime members in the U.S. have unlimited access to watch all three films at no additional charge to their membership. Prime is the exclusive subscription streaming home of the trilogy.

Gale said the first “was a very difficult movie to make,” but there were moments when they realized they might have something special. The films made lots of predictions about life in the 21st century, and while flying cars and ejection seats have yet to hit the market, the film was more accurate about Google Glass, Skype and hoverboards. But as for the trilogy’s enduring popularity: “That was one prediction we never could have made.”