The way in which Doc Brown and Marty McFly met was never shown on-screen in Back to the Future, but their backstory actually adds a much darker subtext to their entire relationship. There are few pairings in the sci-fi genre more iconic than Marty McFly and Doc Brown. The eccentric and brilliant scientist who invents time travel and his hot-tempered teenage sidekick are among the most beloved movie characters of all time, and their trilogy of time-traveling adventures is legendary.
The character of Marty McFly may be Back to the Future's protagonist, but his relationship with Doc Brown is the driving force behind the entire trilogy. Back to the Future introduces Marty as he attends Doc's workshop during his friend's initially unexplained absence, with Doc Brown then introduced at the same time as the franchise's iconic time-traveling DeLorean. This means that the way in which the pair met was never actually shown or explained on-screen - their friendship simply exists, and it serves as the basis for the story.
However, Back to the Future's co-writer once revealed the backstory that he and director Robert Zemeckis decided on for the pair. Doc Brown and Marty McFly met after the latter decided to break into the former's lab, fascinated by his inventions, despite being told for years that Brown was a dangerous crackpot. Doc then discovered Marty tresing, but he was so delighted that Marty thought he was cool that he simply befriended the boy, making him his unofficial sidekick for future experiments. The fact that the pair's friendship began with a criminal act makes the relationship between the slightly unhinged scientist and teenage delinquent even more problematic than it already was.
Marty's Criminal Tendencies Make Doc Brown Even More Dangerous
There are two important aspects to consider as context for Marty and Doc Brown's friendship: Marty is legally a child, and he broke the law by tresing on Doc Brown's property. After being discovered breaking into Doc Brown's lab, Back to the Future's young protagonist was befriended by the very man he'd committed a crime against. From this, one of two things can be surmised: either Doc was so unconcerned with criminality that he saw it as inconsequential or he felt he could benefit from it in some way. It's possible that Doc saw Marty's behavior as a means of manipulating the boy into a form of trust, or potentially that he felt having a friend as morally unburdened as he would come with certain benefits.
This is something that's essentially backed up by the movies themselves. At the beginning of the first Back to the Future movie, Doc Brown is excited to show Marty his newest invention: a DeLorean that's also a time machine. He doesn't hesitate to bring Marty into the potentially dangerous experiment, even knowing that he's crossed a group of dangerous (implied) terrorists. This seems to confirm that Doc Brown isn't at all concerned with Marty's safety or wellbeing and that their meeting was indicative of a darker truth about the convenience of their relationship.
Of course, an eccentric character such as Doc Brown befriending a young and impressionable boy is potentially problematic enough, but Marty's apparent criminal tendencies add another level of vulnerability to the young protagonist that compounds the issue. With the backstory devised by Bob Gale and Robert Zemeckis comes a much darker subtext to the pair's relationship that makes Doc Brown seem particularly dangerous. It's not the only dark Back to the Future theory about the pair, but it's even more troubling as it stems from story devised by the film's writer himself.
