1. Writer and producer Bob Gale came up with the idea for Back to the Future 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 Tom Wilson's 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 detailing that 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?'" she told The A.V. Club. "So that's how I got the first audition for that."