Of all the mysteries and unanswered questions in the Back to the Future universe, there’s one that’s vexed fans most: How did Doc and Marty become such good friends? Some salacious suggestions have been made, but yesterday BTTF co-creator Bob Gale answered the question once and for all. In an e-mail to Mental Floss, Gale wrote that Doc Brown had a reputation around HIll Valley as a crackpot and, troublemaker that he was, Marty decided to sneak into Brown’s lab to see what he was all about. “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.†Okay! That makes sense. Now if he could just explain why George McFly didn’t think it was odd that his son looked just like that guy named Calvin Klein he met in high school. [Mental Floss via Movieline]