1. The script was rejected over 40 times and by every studio.
2. Bob Gale, who co-wrote the script, was inspired to write the story after seeing his father's high school yearbook while visiting him.
3. In the original script the time machine was NOT the iconic DeLorean, but rather a refrigerator.
4. In the refrigerator version of the script, Marty McFly, in a rather dark turn, accidentally time-travels while attempting suicide.
5. The producers decided to use a DeLorean as the time machine in order to keep the joke in the film that it was a UFO.
6. Production designers chose 88 m.p.h. as the speed to achieve time travel because they thought it looked good on the digital speedometer.
7. The lighting hitting the clocktower storyline/scene was added in order to save money.
8. Sid Sheinberg, then-head of Universal Pictures, suggested that they change the name of the movie to Spaceman From Pluto, because he believed a movie with the word "future" in the title would not do well.
Even though Sheinberg was serious the title change — which referenced the barnyard scene in the film where Mr. Peabody mistakes the DeLorean for a UFO — Spielberg played it off as a joke in order to keep the title.
9. Doc Brown was supposed to have a pet chimpanzee named Shemp, instead of his dog Einstein.
10. The set used for Hill Valley had previously appeared in two other iconic movies: To Kill a Mockingbird and Gremlins.
11. When Christopher Lloyd was told that Eric Stolz — who was infamously cast as Marty — was let go, he reportedly had no idea who they were talking about; he had been calling him Marty the entire time and thought that was his name.
12. Lea Thompson was upset about the recasting because at the time Michael J. Fox was mainly a sitcom actor.
13. In order to accommodate Fox's obligations on his TV show, Family Ties, most of the movie was shot at night.
14. Fox was so sleep deprived that he had a freakout during the taping of an episode of Family Ties — he went backstage looking for a video camera prop, thinking he was filming Back to the Future.
15. According to Fox, he really hated filming in the DeLorean due to the fact that the time-circuits box was sharp and would cut up his hand whenever he would change gears.
16. There is an actual backstory on how Marty and Doc became friends. When Marty was about 13 or 14 he snuck into Doc's laboratory, and when Doc discovered him he offered him a part-time job.
17. Crispin Glover hated the ending of the movie. He thought it sent the message that the McFlys were happy only because they had money.
18. Gale and Zemeckis never intended for there to be a sequel(s) to the movie — the open-ended ending with the flying DeLorean was meant to be more of a joke.
19. Zemeckis said there will NEVER be a remake or reboot of the movie in his lifetime.
