Arriving in 1955, Marty discovers he has no plutonium to return. While exploring a burgeoning Hill Valley, Marty encounters his teenage father and discovers Biff was bullying George even then. George falls into the path of an oncoming car while spying on the teenage Lorraine changing clothes, and Marty is knocked unconscious while saving him. He wakes to find himself tended to by Lorraine, who becomes infatuated with him. Marty tracks down and convinces a younger Doc that he is from the future, but Doc explains the only source available in 1955 capable of generating the power required for time travel is a lightning bolt. Marty shows Doc a flyer from the future that documents an upcoming lightning strike at the town's courthouse. As Marty's siblings begin to fade from a photo he is carrying with him, Doc realizes Marty's actions are altering the future and jeopardizing his existence; Lorraine was supposed to tend to George instead of Marty after the car accident. Early attempts to get his parents acquainted fail, and Lorraine's infatuation with Marty deepens.
Lorraine asks Marty to the school dance, and he plots to feign inappropriate advances on her, allowing George to intervene and "rescue" her, but the plan goes awry when Biff's gang locks Marty in the trunk of the performing band's car, while Biff forces himself onto Lorraine. George arrives expecting to find Marty but is assaulted by Biff. After Biff hurts Lorraine, an enraged George knocks him unconscious and escorts the grateful Lorraine to the dance. The band frees Marty from their car, but the lead guitarist injures his hand in the process, so Marty takes his place, performing while George and Lorraine share their first kiss. With his future no longer in jeopardy, Marty heads to the courthouse to meet Doc.
Doc discovers a letter from Marty warning him about his future and rips it, worried about the consequences. To save Doc, Marty re-calibrates the DeLorean to return ten minutes before he left the future. The lightning strikes, sending Marty back to 1985, but the DeLorean breaks down, forcing Marty to run back to the mall. He arrives as Doc is being shot. While Marty grieves at his side, Doc sits up, revealing he pieced Marty's note back together and wore a bulletproof vest. He takes Marty home and departs to 2015 in the DeLorean. Marty wakes the next morning to discover his father is now a confident and successful science fiction author, his mother is fit and happy, his siblings are successful, and Biff is a servile valet in George's employ. As Marty reunites with Jennifer, Doc suddenly reappears in the DeLorean, insisting they return with him to the future to save their children from terrible fates.[a]
Cast appearing in the 1955 portion includes George DiCenzo and Frances Lee McCain as, respectively, Lorraine's parents Sam and Stella Baines, and Jason Hervey as Lorraine's younger brother Milton. Biff's gang includes Jeffrey Jay Cohen as Skinhead, Casey Siemaszko as 3-D, and Billy Zane as Match. Norman Alden plays the cafe owner Lou and Donald Fullilove appears as his employee (and future mayor) Goldie Wilson. Harry Waters Jr. portrays Chuck Berry's cousin Marvin Berry, Will Hare appears as Pa Peabody, and Courtney Gains portrays Dixon, the youth who interrupts George's and Lorraine's dance. James Tolkan portrays Hill Valley high school principal Strickland in both 1955 and 1985.
Following the release of their comedy Used Cars (1980), Gale visited his parents and came across his father's high school yearbook. Gale questioned whether he and his father would have been friends had they attended school together. He did not think so but realized he could test his theory if he could travel back to a time when he and his parents were a similar age. He shared the idea with Zemeckis, who recalled his mother's childhood stories were often contradictory.
Gale and Zemeckis began a draft in late 1980. They sketched and acted out each scene to help develop the dialogue and actions. They believed many time travel films focused on the past being immutable and wanted to show the past being altered and the impact those changes would have on the future. In the draft, video pirate Professor Brown builds a time machine that sends his young friend Marty back to the 1950s where he interrupts his parents' first meeting. In September 1980, Gale and Zemeckis pitched their idea to Columbia Pictures president Frank Price, who had liked Used Cars and was keen to work with the pair. Gale recalled having to rein in Zemeckis' enthusiastic pitch before Price had time to change his mind. Gale and Zemeckis completed the first draft for Price on February 21, 1981, but Price believed it needed significant refinement.
Gale and Zemeckis drew humor from the cultural contrasts between 1955 and 1985, such as Marty entering a 1955 soda shop while wearing 1985 clothing. The shop owner asks Marty if he is a sailor because his down vest resembles a life preserver. They also identified conveniences of 1985 that Marty had taken for granted, but would be denied in 1955. Gale and Zemeckis struggled as they were in their 30s and did not particularly self-identify with either era. They were inspired by the All-American aesthetic of films by Frank Capra featuring white picket fences and exaggerated characters like Biff, The Twilight Zone, science-fiction films, and books by Robert Silverberg and Robert A. Heinlein. The romantic relationship between 1955 Lorraine and her future son was one of the more difficult writing challenges. Gale and Zemeckis attempted to take the concept as far as possible to keep the audience on edge. They believed it had to be Lorraine who stopped the relationship; she remarks that kissing Marty feels like kissing her brother. Gale jokingly said no one asked how she could make that comparison, but that audiences would accept it because they did not want the relationship to happen. The second draft was completed by April 7, 1981.
Fox's first day on set was January 15, 1985. He filmed Family Ties during the day before traveling to the Back to the Future filming location. Often, he would not return home until early the following morning, and on weekends, the schedule was pushed back further as Family Ties was filmed in front of a live audience. The teamsters dropping Fox at home regularly had to carry the actor to bed. This continued until April, when Family Ties finished filming. Gale said Fox's youth meant he could cope with less sleep than usual; Fox described it as exhausting, but worth the effort. Further into the filming schedule, Fox was energetic during his scenes but struggled to stay awake off set. He ad-libbed some lines when he forgot the intended dialog, and recalled looking for a camcorder on the Family Ties set, before realizing it was a prop on Back to the Future. He also had to learn to mimic playing the guitar and choreographed skateboarding routines taught by Per Welinder and Bob Schmelzer.
Deleted scenes include: Doc looking at an issue of Playboy, remarking the future looks better; a scene of 1985 George being coerced into buying a large amount of peanut brittle from a young girl; a scene of young George being trapped in a phone booth by the man who interrupts his dance with Lorraine; and the scene of Marty pretending to be "Darth Vader", which was shortened. Zemeckis considered cutting the "Johnny B. Goode" performance because it did not advance the story, but test audiences reacted well to it. There is a dispute if a shot of Stoltz's hand is in the finished film in the scene where Marty punches Biff. Gale noted it is impossible to tell without checking the original film negative, which would risk damaging it. The final 116 minute cut was completed on June 23, 1985. Universal Studios took out a full-page advertisement in Variety magazine, thanking the post-production crew for completing their work on time. The final budget was $19 million.
The tight schedule affected the special effects' quality. Ralston was disappointed by the scene where Marty's hand fades away as his future is altered. Fox was filmed separately from his hand and the two were composited together; the hand was filmed with a wide-angle lens, making it appear too large and it had to be scaled down. Zemeckis wanted a subtle fade, but it resulted in a small circle of the hand fading away and there was no time to fix it. In the same scene, Marty and his siblings fade away from a photo. ILM found it difficult to fade the photo's individual aspects, especially as it was moving on the neck of a guitar. A replica of the guitar neck was constructed at four times the normal size; the guitar strings were made of cable up to a quarter-inch thick. An 11 by 14 inch aluminum plate was attached to hold the enlarged photograph. ILM used a version of the photo without Marty or his siblings and individually pasted each character into the photo. When this failed, four different photos were used: one containing the background, and one for each McFly sibling. A mechanical camera cycled through each photo and printed it to the film. The enlarged guitar was moved around to add to the realism.
Initially, Back to the Future was scheduled to be released in May 1985, but was pushed back to June 21, the earliest Zemeckis could have the film ready. The delay caused by Stoltz's replacement pushed the release back to July 19, and later to August. Sheinberg moved the release date forward to July 3, giving it an extra 16 days of theatrical screen time during the industry's most profitable period of the year. The move offered about 100,000 extra screenings, together worth an estimated $40 million. He said he also wanted to avoid the negative perception of films released later in the summer period; other blockbuster films were usually released early. The change required renegotiations with theater owners to secure screens in an already-crowded marketplace. In some cities, it was legally required that exhibitors be shown a film prior to purchase; an unfinished cut of the film was shown to theater owners and young test audiences. They described it as lesser than E.T. the Extra-Terrestrial or Ghostbusters, but still a guaranteed box office hit. Fox was unavailable for promotional work because he was filming Family Ties Vacation (1985) in London. 2b1af7f3a8