Revealing mistake: In the scene where Doc Brown is following Biff into the tunnel, as Marty starts to pass between the cars on his hoverboard, one of the wheels on the rig supporting the hovering DeLorean is visible. (01:30:30)
Back to the Future Part II (1989)
Ending / spoiler
Directed by: Robert Zemeckis
Starring: Christopher Lloyd, Michael J. Fox, Lea Thompson, Thomas F. Wilson, Elizabeth Shue
After causing Biff to crash into (another) manure truck, Marty finally recovers the sports almanac from Young Biff in 1955 and burns it, restoring the timeline to its proper state. The DeLorean, which is flying overhead, is struck by lightning, sending it and the Doc through time. Thanks to the Doc's hind/foresight, he sends a telegram ahead to Marty's exact location and time, assuring him of his safety in his new location--1885! Marty immediately heads to where the 1955 Doc has sent himself (Marty) into the present (remember that this happened in the first movie), and tells him that he's "back from the future". The shock is too much for the scientist, and with a "Great Scott!", he passes out. To be concluded...
Artp
More mistakes in Back to the Future Part II
Biff: Go ahead, kid. Jump. A suicide will be nice and neat.
Marty: What if I don't?
Biff: [raising gun] Lead poisoning.
Marty: What about the police, Biff? They're gonna match up the bullet with that gun.
Biff: Kid, I own the police. Besides, they couldn't match up the bullet that killed your old man.
Marty: You son of a...
[Biff pulls back on the gun's hammer.]
Biff: Suppose it's poetic justice. Two McFlys with the same gun.
More trivia for Back to the Future Part II
Question: In the alternate 1985, there is an alternate Biff, Lorraine etc. Shouldn't there also be an alternate Marty and Doc?
Answer: Doc would most likely not have been seen by anyone, as the time he spent in the alternate 1985 was primarily inside the DeLorean, at a boarded-up library, graveyard, and his lab (and all at night too) so most likely not spotted by the public.
Even if someone had seen Doc, it could've been dismissed as someone who looks like him. Even if they did report his escape, someone would either call or go to the asylum and verify Doc was still there.
I also don't think that Doc Brown ever achieved celebrity status prior to his being committed, so how would the average person even recognize him as some obscure scientist who was put away?
Answer: Yep, and there is, but they're both elsewhere. Doc's been committed to an asylum somewhere. When Marty first meets the alternate Biff, Biff tells him that he's supposed to be in Switzerland at boarding school - that's where the alternate Marty is.
Tailkinker ★
Wouldn't someone probably see Doc and report that he escaped from the asylum?
Maybe, but no way to be sure, and they're not around long enough for that to be an issue anyway.
Jon Sandys ★
That's why he stayed hidden most of the time (such as in the abandoned lab).