In BTTF: why is Doc in such a hurry at the end of the film to take Marty to 2015 to fix a problem with his kids, ASAP? He’s got a Time Machine... he could literally leave at any time, he could wait a day or two, catch up with Marty, take more time to set up a plann. I can’t believe that Doc would’ve been that impatient, knowing what had just happened.
Jennifer was there, so Doc dragged her as long as well, because it said "it affects her, too". However, at the beginning of BTTF2, Doc knocks her out so that she won’t get in the way. He really didn’t want her in the first place/ he never really wanted her to come along.
At the end of BTTF 3, the DeLorean Time Machine is destroyed by a train. The train can be seen stopped much further down the tracks. There’s debris everywhere. Marty immediately leaves the site to go find Jennifer on the front porch; they hop in his Toyota truck, Marty almost gets into a wreck (but avoids it, etc). Then they go back to the train tracks where the accident happened and… nothing. There’s still debris everywhere, but there’s no police cars, the tracks aren’t even closed off, there’s no emergency personnel on scene, etc. I get it that this may have been an hour or two after the DeLorean was destroyed, but it’s still the middle of the same day, the sun is still up.
And then Doc Brown appears in his new train Time Machine, and they’re still nobody else around! This is not a remote train crossing, it's on the edge of a subdivision/ development. Where is everyone?! How are Jennifer and Marty the only observers?