"Roads? Where we're going, we don't need roads." But you will need a streaming account if you want to rewatch this iconic '80s flick.

Released in July 1985, Back to the Future went on to become the highest grossing film of the year, making over $389 million and going on to become a beloved movie franchise. 

And in honor of the epic film, starring Michael J. Fox and Christopher Lloyd, turning 38 (!) this year, we're hopping in the DeLorean, checking the plutonium levels and hitting 88 miles per hour to reveal some surprising secrets about the Robert Zemeckis-directed film franchise.

Like, the fact that another '80s star originally sported Marty McFly's Nike Mags before Fox took over several weeks into filming. (You can see the OG Marty in one scene, by the way!)

Plus, Lloyd originally passed on the chance to play Doc Brown, with a Jurassic Park actor nearly landing the iconic part before Lloyd changed his mind.

From the stars who were almost cast as Marty and Doc Brown to the actor who sued the studio, here are 30 behind-the-scenes facts you might not know about the beloved Back to the Future trilogy...

1. Writer and producer Bob Gale came up with the idea for the movie while looking through his father's high school yearbooks during a visit with family and discovering his dad was the president of his graduating class. As he put it to Esquire, "I wondered whether I would have been friends with my dad in high school."

2. For years, multiple studios passed on the script, more than 40 rejections in total. Among them: Disney, with Gale claiming they said, "Are you guys out of your minds? You can't make a movie like this here. This is Disney, and you're giving us a movie about incest!"

3. Not a fan of the title, Universal Pictures head Sid Sheinberg suggested the name be changed to Spaceman From Pluto.

4. John Cusack and Johnny Depp originally auditioned for the role of Marty McFly, but C. Thomas Howell was the finalist for the role, ultimately losing out to Eric Stoltz.

5. Five weeks into filming, the filmmakers realized Stoltz wasn't the right fit for the role, with Gale explaining to The Guardian, "The humor just hadn't been coming through with Eric. The studio weren't happy exactly, but they'd seen the footage so they bit the bullet."

6. Director Robert Zemeckis was the one to deliver the news to Stoltz, with the filmmaker recalling in the book Blockbuster that it was "the hardest meeting I've ever had in my life and it was all my fault. I broke his heart."

7. Reshooting all of the scenes Stoltz had already filmed added a reported $4 million to the movie's budget.

8. Because Michael J. Fox was the original first choice for Marty, the filmmakers worked with the team at his hit sitcom Family Ties to make sure they could have him as their leading man. "We would've danced naked on his desk to get Michael J. Fox, so of course we said, 'Yeah, sure, we'll adjust our shooting schedule,'" Gale told The Hundreds blog.

9. Fox's filming schedule was intense: He would shoot Family Ties during the day and then go right to the Back to the Future set from 6:30 p.m. to 2:30 a.m., averaging five hours of sleep a night. "It was my dream to be in the film and television business, although I didn't know I'd be in them simultaneously," Fox said during a TV special. "It was just this weird ride and I got on."

10. There is one scene with Stoltz still in the film. Though you can't see his face, it's Stoltz who punches Biff at the diner. 

11. In the original script, Doc Brown was called Professor Brown, with a studio executive recommending the change. 

12. Jeff Goldblum auditioned for the role of Doc Brown, according to Gale, who said, "The only other guy we really seriously considered for Doc Brown was Jeff Goldblum. Jeff came in, and…I'm certain we talked about John Lithgow, but I don't remember if he ever actually came in, or if we met him. But I vividly remember meeting Jeff and liking him."

13. Christopher Lloyd almost passed on the iconic role, hoping to do a play in New York instead. But he credited his wife, Carol, who "reminded me that I always told myself never to turn anything down without at least checking it out."

14. In an interview with the Seattle Times, Lloyd revealed his two inspirations for Doc: Albert Einstein and Philadelphia orchestra conductor Leopold Stokowski, who had white hair. 

15. One of the reasons for Doc's hunched over stance? To help with the seven-inch height difference between the two leads. 

16. The Office's Melora Hardin initially snagged the role of Marty's girlfriend Jennifer, but was recast before she even began filming after Fox replaced Stoltz. The issue: At 5-foot-5, she was an inch taller than Fox.

17. Though Claudia Wells originally played Jennifer in the first film, she retired from acting after her mother was diagnosed with cancer. Elisabeth Shue took over the role for the remaining installments. 

18. Originally, the studio was hoping Doc's car would be a Ford Mustang, with the company paying for the placement, but Gale refused, telling AdWeek, "I said, 'No, no, no, Doc Brown doesn't drive a f--king Mustang.' It had to be a DeLorean." 

19. Huey Lewis, who wrote the hit songs "The Power of Love," and "Back in Time" for the film, makes a cameo as one of the judges in the band audition.  

20. Lewis originally declined to work on music for the movie when he was approached by the director. 

21. In an early draft, the time machine was set to be a refrigerator, but Zemeckis was worried children would accidentally lock themselves in refrigerators, so it was changed to a car.

22. Originally slated to open in August 1985, test audiences reacted so positively to the movie that the studio moved the release date up. Back to the Future hit theaters nine weeks after completing production. 

23. Crispin Glover, who played Marty's father George McFy, didn't return for the sequels due to contract disputes. He later filed a lawsuit after filmmakers used footage from the first film and put a mold of his face on another actor "in order to fool audiences into thinking I was in the movie," he said on The Opie and Anthony Show. 

Ultimately, a settlement was reached, with The Hollywood Reporter reporting he received $760,000 at the behest of the company that insured Universal.

24. Lea Thompson credits her turn in 1984's The Wild Life for landing her the role of Lorraine, Marty's mother, because "they were looking at Eric Stoltz for Marty McFly, and they were, like, 'Who's that girl?' So that's how I got the first audition for that," she told The A.V. Club.

25. In the original script, Lorraine's name was Meg. 

26. To achieve Lorraine's 1985 look, Thompson's prosthetic makeup took three and a half hours to apply. 

27. In 2015, footage of Stoltz as Marty was released for the first time in a documentary included on the 30th anniversary Blu-ray set. "We wanted to soft pedal that," Gale said of the decision to release a small look at his turn performance. "We didn't want to make Eric feel bad."

28. Back to the Future: The Animated series ran for two seasons, airing on CBS from 1991 until 1992.

29. In March 2020, the musical adaptation of Back to the Future made its debut in England, with Olly Dobson as Marty McFly and Tony winner Roger Bart as Dr. Emmett Brown.

30. Zemeckis and Gale are firmly against the idea of a fourth film, with the director saying on a Zoom cast reunion that, "If I had an idea which I could have pitched to Bob [Gale] with a straight face, we would have made it."

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