"When this baby hits 88 mph, you're gonna see some serious s***."
I haven't done anything related to Back to the Future for almost two weeks. So, I'll do a theory on the movies that says Doc Brown was suicidal.
So here's the theory...
A few minutes into the movie, Marty meets up with Doc at the Twin Pines Mall to test out the DeLorean time machine for the first time. Doc puts his dog, Einstein, in the time machine with a stopwatch. He drives the DeLorean back and says the iconic line you see above.
Doc begins to accelerate the wheels without the car actually moving. He knows that he's gone over 30 years repeatedly inventing and inventing with no prior success. He knows that if this very first test drive doesn't work, his life would be useless.
The wheels accelerate to about 63-64 mph and he allows the wheels to run. Yeah. Why would he do that? Why would he allow a car to drive directly toward himself and an innocent 17-year old. He was intentionally accelerating the car to 88 mph and again, he was driving it directly toward himself, fully aware that he was doing it. He was so depressed about his failure that he was willing to murder himself, a teenager, and possibly his dog. In fact, he may have been trying to prove to himself that he was good at something: failure.
We'll call this Doc "Doc A". He's the Doc that didn't have Marty in his life in 1955. And this Doc A finally gets what he wishes by getting killed by Libyans.
Later, Marty travels to the year 1955 and meets a younger Doc. Earlier that day, he had injured his head while trying to hang a clock in his bathroom.
Hey, Doc! Ever heard of a watch?
Why would you need a clock in your bathroom? I mean, sure, we see the clock in his bathroom later, but Doc probably tried to hang himself, but failed and hit his head on the toilet. That's how he came up with the Flux-Capacitor. He meets Marty later that day and he is now a "Doc B", who uses a bulletproof vest to prevent himself from being killed by Libyans and finds love. And that's the Doc we would prefer, because the Doc at the beginning of the series was a lunatic scientist whose only friend was a 17-year old male.
And that's the theory!
I didn't come up with this theory, but I just decided to share it because I thought it was very famous and a good fan theory.