Crazy Is as Crazy Does
There's nothing more obnoxious than the overblown "You're so crazy" comment when you do perfectly natural things like pick out all the blue M&Ms out of a bag because they taste the best, or think Steve Buscemi is sexy, or maintain the loud opinion that Sugar Ray will eventually be remembered as being as genius as Beethoven.
But even if these weren't completely sane things to do (this is your cue to pat our head and say, "Yes, yes. Perfectly normal.") they wouldn't be crazy.
Crazy would be strapping an odd-looking contraption onto the head of a complete stranger in an attempt to read his mind. Or trying to rip plutonium off a bunch of heavily armed nationalists. Or running out of a room screaming, "1.21 jigowatts! 1.21 jigowatts!" while tearing at your wild mass of white hair.
Yeah, Dr. Emmett "Doc" Brown is entirely his own brand of crazy. It's the reason he only has, seemingly, a single friend, and why he's basically an outcast from the rest of society. He's clearly good at what he does—it isn't likely someone's going to draw up the blueprints for a working time machine by accident—but there's a definite madness to his methods.
First off, he looks crazy. If we were walking down a sidewalk and this nutso started walking toward us, we'd cross to the other side of the street. He's sporting a hairstyle only worn by Albert Einstein and a handful of serial killers, his eyes are bugging out of his head like some kind of cartoon character, and the guy wears goggles like they're going out of style.
But more than his appearance, it's the way he behaves that would probably lead us to believe that the loony bin was short one loony. His movements are spastic and erratic, he screams more often that he speaks, and he really likes to play with his hair.
So why does Marty need all this crazy in his life? Well, look at his family. Check out his browbeaten father, who is a typical slave to The Man. Or his desperate housewife mother. His brother and sister who couldn't be any more normal, or less interesting.
But Marty doesn't want typical. He has dreams of being a rock star, of breaking away from the daily grind and living a life outside of small-town America. He craves excitement and welcomes "crazy," which is why it doesn't bother him that his best bro is kind of like an extra from One Flew Over The Cuckoo's Nest.
One Smart Cookie
If Doc were only crazy, he and Marty probably wouldn't have much of a friendship. (Oh, BTW, it's quietly established why Marty and the Doc are friends in the film's first scene: Marty uses Doc's equipment as a sound system for his guitar.) If all Marty was seeking was someone on the fringes of society, he'd be just as well off making nice with that drunk, homeless guy who wakes up on a park bench at the end of the movie.
But Doc isn't just crazy. He's also crazy smart.
Okay, so quite a few of his inventions turn out to be duds. But he's not a complete hack. The guy invents time travel, for goodness sake. And yes, it took a fall off the toilet and a bump on the head to give him his "vision." But he's determined:
DOC: It's taken me almost thirty years and my entire family fortune to realize the vision of that day.
Yeah. This guy has devoted himself absolutely to creating his time machine. Procrastination is not one of Doc's vices.
While Marty may have his fair share of street smarts, he's not a brainiac by any stretch of the imagination. So this is a little bit of opposites attracting. But it's also because he wants to be smarter. He takes an active interest in Doc's experiments; he doesn't just consider him a buddy.
Don't be fooled by his impressive string of consecutive tardy passes—there's a real desire within Marty to better himself, and sitting at the feet of a guy like Emmett Brown is one possible way to accomplish the feat.
Within the framework of the story, Doc's braininess comes in handy for more than just creating the time machine in the first place (without which there wouldn't have been much of a story). He also has a large hand in helping Marty figure out how to get his parents together:
DOC: Now remember, according to my theory you interfered with your parents' first meeting. They don't meet, they don't fall in love, they won't get married and they won't have kids. That's why your older brother's disappeared from that photograph. Your sister will follow and, unless you repair the damages, you'll be next.
Not only does he somehow understand the magical disappearing photo angle of time-travel, he knows how to generate the electricity he needs to fuel the DeLorean, and how to preserve the space-time continuum by not revealing too much about the future (even if, ultimately, he doesn't listen to his own good advice).
A Friend 'Til the End
So are Doc's sizeable noggin and unusual antics all he's good for?
Of course not. When you boil everything down, this is really a buddy movie. It's got plenty of bells and whistles to distract from that idea, but without Doc and Marty's unconventional friendship, nobody goes back in time and nobody needs to find a way to get back.
Just as we root for Marty because he's a basically good guy who looks out for his friends and loved ones, we root for Doc for the same reason. When the Libyans are coming up on them, Doc separates himself from Marty and takes those bullets, in hopes that his friend will manage to survive.
When Marty shows up in 1955, Doc exerts a tremendous amount of time and energy to help this kid—who he doesn't know from Adam—get back to where he came from. And their good-bye, which takes place only one week after 1955 Doc meets Marty, is sincerely heartfelt.
Even as the movie ends, Doc is still concerning himself with Marty's welfare by checking in on his future self and kids. He's like a weird-looking, time-traveling, gadget-loving Fairy Godmother.