Here’s the answer to question more than 25 years in the making: Just why did Marty spend so much time hanging out with some crazy old scientist anyway?
At the start of the original Back to the Future, Doc Brown and Marty McFly are already friends. When we first meet Marty he’s hanging out in the Doc’s lab, feeding the dog, playing with the elderly scientist’s instruments. This might make seem natural if Marty were some sort of science geek, but he’s not. Instead he’s kind of a black sheep, rebel, wannabe. Not the type you usually see hanging around in labs.
The question of just why Marty spent so much time hanging around with Doc Brown in the first place was raised on Mental Floss and not only did they find an answer, but they found an official answer from one of the co-creators of the entire Back to the Future franchise, Bob Gale.
Gale says that even though it isn’t in the movie, he and director Robert Zemeckis had worked out a back story for the two and they all understood how Doc and Marty’s relationship came about. Here’s how Gale explains it:
For years, Marty was told that Doc Brown was dangerous, a crackpot, a lunatic. So, being a red-blooded American teenage boy, age 13 or 14, he decided to find out just why this guy was so dangerous. Marty snuck into Doc’s lab, and was fascinated by all the cool stuff that was there. when Doc found him there, he was delighted to find that Marty thought he was cool and accepted him for what he was. Both of them were the black sheep in their respective environments. Doc gave Marty a part-time job to help with experiments, tend to the lab, tend to the dog, etc. And that’s the origin of their relationship.