When people watch the Back to the Future films, you are always concentrated on Marty's famous line, "This is heavy," Doc's antics and "Great Scott!", Biff crashing into manure, and Lorraine. But I don't think you ever noticed how negligent Doc can be. Here's what I'm talking about:
Oh, and spoilers. Duh.
At one point, Doc mentions that he had stolen plutonium from Libyan nationalists that had wanted him to build them a bomb. The plutonium would eventually be what provided the 1.21 gigawatts of energy to the time machine. But right when Doc is about to travel to the year 2010 (25 years after 1985), the Libyans find him and shoot him to death. But here's what you probably didn't notice:
How did the terrorists even know that Doc was going to be at the Twin Pines Mall at 1:30 in the morning?
I mean, maybe they could have tracked Doc to Hill Valley, but how the hell did they know exactly where he was at the exact time? It seems like Doc worked with the terrorists to try and kill him. And what if Doc had remembered to pack extra plutonium and left for the future? The terrorists would find Marty and Einstein there and kill them. And what if Marty hadn't been able to get away in the DeLorean? After killing Marty, they could use the DeLorean to travel back in time, and kill everyone important and historical.
He Pointlessly Sent Einstein into the Future
Why did Doc test the DeLorean by sending Einstein one minute into the future? Why couldn't he have just put the stopwatch in there and that would have worked just fine? Why did Einstein have to be in there?
Knowing About Your Destiny
In 1955, Marty knew Doc would get shot by the terrorists, so he gives Doc a letter warning him about his death so that he could survive. However, Doc rips up the letter because he believed that you should never know too much about your own destiny, and if you do, you could endanger your own existence.
But sometime between 1955 and 1985, Doc tapes the letter back together, reads it, and survives because "I figured, what the hell?"
Then, Doc takes Marty and Jennifer to 2015 and Doc clearly knows about how Marty participated in a race with Needles, causing him to run into a Rolls Royce, causing him to injure his hand, and causing him to give up on his music career, as he can no longer play guitar with the injured hand. Doc knows this because in Part III, he tells Marty that he can't keep losing control when someone calls him a name, because that's what would cause the accident in the future.
So, knowing about your destiny is okay if you can survive, but it's not okay if your friend gets the music career he always wanted?
He Burned Down His Mansion for the Time Machine
After Doc puts 1955 into the time circuits, he says that it took 30 years and his entire family fortune to build the time machine. And as we can see above, he destroyed his entire mansion just so that he could make the time machine. And that's not fake. It appears in the opening scene of the first film when we look into Doc's lab.
Also, when they go into 2015, he says he went to a rejuvenation clinic and they took out the wrinkles, did a hair repair, changed his blood, and replaced his spleen and colon, adding 30-40 years to his life. Where'd he get the money for that?!
The Train Time Machine
Starting in Part II, he begins to regret ever building a time machine and wants to destroy it as soon as he can, because of all the terrible things that a person can do with it. He says that he would rather study the other great mystery of the universe: women.
But then, in Part III, the DeLorean time machine is destroyed, causing Marty to be in 1985 and Doc to be stuck in 1885. However...
He builds a brand new freakin' time machine. And then at the end of the series, he travels to somewhere else. Where's he gonna go? I mean, I thought that he had had enough with the time traveling and all that stuff and yet here he is, with a brand new time machine that he's going to use to make Back to the Future Part IV. Then, he's going to call THIS time machine infernal and he's gonna want to destroy THIS time machine.
Well, my work here is done.