Trivia: Eric Stoltz was originally cast as Marty. After filming quite a few scenes they realised his acting style was too dramatic for the humor desired, so they cast Michael J Fox (who they couldn't originally get because he was busy with the TV show Family Ties). Filming was on weekends and nights around his TV schedule and using his double at other times.
Trivia: In the first scene when Marty arrives at Doc's place and the camera pans across all the clocks, one particular clock has an hour hand and a minute hand with a man hanging from it - foreshadowing Doc's perilous scene hanging from the clock tower. The hanging man isn't Doc, but the silent movie star Harold Lloyd, in a reference to him in Safety Last. Sadly though, Harold and Christopher aren't related. (00:01:35)
Trivia: Melora Hardin was originally cast as Jennifer Parker (Marty McFly's girlfriend). She was later let go when Michael J. Fox replaced Eric Stoltz (who was originally cast as Marty McFly) because she was much taller than Fox and director Robert Zemeckis thought that they would look odd together on screen.
Trivia: In 1985 Doc is living in what was in 1955 his garage/workshop after the Brown mansion burned down (note the newspaper clippings at the start). Looking at the appearance of it in the different years you can see that they are same place. This also explains why Marty looked at the garage so intently when he first arrives at Doc's house in 1955, he must have been surprised to learn this. (00:06:05 - 00:47:55)
Trivia: The original idea for the time machine was that it would be in the form of a refrigerator.
Trivia: Originally, the beginning of the film started out with Marty sitting in class at school. He is caught listening to his walkman and sent to Strickland's office, causing him to be late for the battle of the bands audition. This was filmed with Eric Stoltz, who was cast first as Marty. When Stoltz was fired and Michael J. Fox was hired, the beginning was quickly rewritten to start in Doc Brown's place, with Marty being late for school.
Trivia: At 1:15 am on October 26, 1985, a crowd of people showed up at the mall that was used as the Twin Pines/Lone Pine Mall for the movie, which had come out months before. They wanted to see if anything peculiar was going to happen. Nothing did. A group of devotees have shown up at the same location (Puente Hills Mill in Rowland Heights, CA) at the same time every year since.
Trivia: RQ magazine, a magazine for librarians, can be seen at the head of Marty's bed. On release many librarians noticed it and wrote to writer Bob Gale asking what the significance was of placing this magazine in shot. Sadly he replied saying there was no hidden meaning - a set decorator had simply grabbed the first pile of magazines they saw from the prop department without knowing what they were. (01:46:40)
Trivia: The amplifier that Michael J Fox blows up at the beginning is labeled as being a CRM-114. This is a reference to Dr. Strangelove, in which the B-52 crews receive their orders over a CRM-114. It was also the serial number of the Jupiter explorer in 2001: A Space Odyssey (1968) also directed by Stanley Kubrick. (00:03:05)
Trivia: When Marty returned to 1985, Red was on a park bench that had the logo for California Raisins. The California Raisin Board paid the producers $50,000 for this product placement. However, since it was so dark and dirty, and since Red was covering up most of the logo, half their money was refunded. (01:41:50)
Trivia: Director Robert Zemeckis and producer Bob Gale's first choice for the part of Marty was Michael J. Fox. When he was unavailable due to scheduling conflicts, their second choice was C. Thomas Howell but the president of MCA wanted Eric Stoltz for the part. Six weeks into production, Zemeckis fired Stoltz and was then able to get the then available Michael J. Fox for the part. Fox was available weekends and nights while still acting on weekdays for the popular TV show "Family Ties."
Trivia: In case there is any confusion a Gigawatt (not Jigawatt) does exist, it means 1 billion watts. So, the power required for the flux capacitor is 1.21 billion watts. Whether it could be channeled down cables that easily is another matter.