'Back to the Future' Screenwriter: I Never Could Have Predicted Smartphones

"Part of what makes the movie still so watchable, even as goofy as some of the stuff is, is that everybody understands that we're having fun with it," said Bob Gale, screenwriter and co-producer of the trilogy.

Of all the futuristic ideas screenwriter Bob Gale came up with for Back to the Future Part II, there is one piece of modern technology he never imagined possible in 1989: the smartphone.

"It's the Swiss Army Knife of today," he said. "The fact that everyone can have one device that's a computer, that's a camera, that's a recording device, that's a calculator, that's a flashlight ... we didn't think of that."

In an interview with THR on the Universal Studios backlot, Gale talked about the future he and director Robert Zemeckis envisioned for their character Marty McFly, who will arrive on Oct. 21, 2015, according to the film.

Some of the ideas for gadgets were just the Oscar-nominated pair goofing around — like the food hydrator — but other inventions Gale knew would be a reality in the not-too-distant future, he said.

Added Gale, "I would have bet that the flat-screen TV and the Skype-like communication — I would have put money that we would have that."

Gale, a co-producer of the trilogy, also knew that people in 2015 would be nostalgic for the '80s, he said. "You're always going to be nostalgic about what happened 30 years ago."

In recent years, there has been a push to develop the technology seen in the film, especially hover boards and power shoelaces. Just in the past week, Pepsi announced it will make a limited-edition bottle from the film, and Universal released a fake trailer for Jaws 19.

Gale is happy his art has inspired reality, but he said he is shocked some inventions that were gags then actually exist now.

"The fact that we have drones that can take news pictures — now that was just a joke," he said. "We weren't seriously thinking about how that technology would work, but wow," said Gale. "They don't walk our dogs yet, but that'll happen."

There was one aspect of the future that Gale and Zemeckis purposely avoided: the music.

"That was a very deliberate choice," said Gale. "That was one we knew we would get wrong and that when people would watch the movie much later on, it would make everyone groan."

Stars Michael J. Fox and Christopher Lloyd never balked at any of the futuristic ideas during production, said Gale.

"Part of what makes the movie still so watchable, even as goofy as some of the stuff is, is that everybody understands that we're having fun with it," said Gale. "We're not saying, 'We're going to seriously try to predict what life is going to be like in the year 2015,' no."

As for the technology Gale wishes existed — that's fusion energy, he said.

"That would mean that we would have limitless energy that would be extraordinarily cheap," he said. "That would solve so many problems in the world, but I don't think that's going to happen."

Now that 2015 has arrived, Gale is thinking about what technology will exist in the next 30 years.

"We've got a serious doctor shortage that is on the horizon," he said, "but when we're able to have devices at clinics or even at home that can instantly analyze your blood, take your vital signs, do a retinal scan right there ... they'll be able to do a better diagnosis with all this equipment than a regular doctor would be able to do."

The Back to the Future 30th Anniversary Edition comes to Blu-Ray and DVD on Oct. 20.