Question: When Doc comes back at the end, it's to say goodbye to Marty, but what's stopping him from just staying in 1985 with Clara and their two sons? I mean, before Clara turned up at the train in 1885, Doc was all set to go to 1985 with Marty, and then when Clara showed up, Doc said that they'd have to bring her too because there wasn't much time left before the train ran out of track, and he couldn't just let her perish. So why doesn't he just stay in 1985 - that's where he was going to go before Clara turned up, and now that he has her, and a family, why not just settle down in 1985?
Answer: Doc actually explains in Back to the Future: The Game. I recommend playing that as it continues where part 3 left off. Doc actually tells Marty that he wanted him to live his life without the complications of time travel. So he left and moved to another time period. I don't want to spoil the rest of the game if you haven't played it but it gets into most of your question in the game definitely should give it a playthrough.
Question: What exactly was the issue with the telescope? Clara states that if you turn the dial one way, the image turns fuzzy, but if you turn it the other way, it becomes clear. I thought that was how telescopes (and binoculars, for that matter) worked, as you have to adjust the focal point. Is she just using it as an excuse to see Doc, or does she just not have a clue how telescopes work?
Answer: It was an excuse to see Doc. When Clara says, "if you turn the dial this way, everything is fuzzy," she's slyly putting her arm around Doc's shoulders. Doc is the one who says everything becomes clear when he realizes what's happening.
Question: Why does Jennifer at the end never seem surprised or even question Marty over why he is dressed as a cowboy (even though Marty's family does and Dave even comments on it)?
Answer: Not sure why it's suggested that Jennifer knew about Doc and Marty's time-traveling. She immediately wakes up and tells Marty that she "Had the worst nightmare," and then in the truck, she starts saying, "That dream I had seemed so real. It was about us, and you got fired." She then asks Marty to confirm if it was a dream. Marty only had to inform her and show her the remains of the DeLorean because she still had the "You're Fired" paper in her pocket, neither of which Marty or Doc knew she had. At that point, it would've confirmed to her that she wasn't dreaming.
Answer: Jennifer was already aware of Doc and Marty's time-traveling, while his family knew nothing about it. She'd been to the future with Marty and Doc, and previously saw Doc wearing futuristic clothes. There's no reason she should be surprised, and Marty quickly updated her about everything soon after.
Question: Why does the bartender tell Doc "you know what happened last 4 of July" when he offered him a shot of whiskey if he's only been there 1 week?
Answer: In the letter Marty gets, Doc says he's been living in 1885 for the past 8 months. It's dated September 1. Marty in 1955 finds out that Doc dies one week after he wrote the letter (Sept 7th), not one week after he got to 1885. Marty then goes to Sept 2, 1855, one day after Doc wrote the letter.
Question: I have a question, I don't know if it's true or not but I have heard about this for years after Part III was released. Had Crispin Glover decided to do the sequels, would he have had the role of Shamus McFly in Part III, or once Glover turned down the sequels, then it was decided that Michael J. Fox would play the part of Sheamus once Part III was greenlit? Or was it always going to be Fox playing the role of Sheamus regardless if Glover came back for the sequels or not?
Answer: In an interview, actor Jeffrey Weissman (the actor who replaced Glover as George McFly) mentioned Glover was slated to play Shamus since Lea Thompson, who played Lorraine (Marty's mom) also played Maggie (Shamus' wife). So it made sense the Mom and Dad would play the great-Grandparents. However, without the heavy makeup and prosthetics to look like Glover, the film makers thought having Weissman playing the role would look too unrecognizable that the audience wouldn't know who he was. In a side note, the scene of elderly George hanging upside down in BTTF 2 was written with Crispin Glover in mind as payback.
Question: When Seamus is telling Marty that he'll take him to the train station the next day and give him a new hat, it shows Maggie doing the 'Sign of the Cross'. Was she unhappy with Seamus helping out a "stranger"?
Answer: She was blessing Marty because, by wearing one of those hats, it was basically a giant "kill me" sign for Mad Dog. When Mad Dog first enters the saloon, he mistakes Marty for Seamus based on Marty's "dog-ugly hat".
Answer: It's not about Marty. Maggie is angry because Seamus constantly buys hats, which she considers wasteful and frivolous when they have so little money. Religious people will make the sign of the cross when they feel they need "forgiveness" for thinking angry or unkind thoughts or asking God to help them control their temper.
Question: Doc seemed hell-bent on destroying the DeLorean. So why did he go to the future and get a hover conversion done on the train? Why didn't he just build the train, return to his own time and then destroy the train?
Answer: He didn't return to the Old West, both of them had a desire to go to the final frontier. Their favorite author is Jules Verne, who wrote "From Earth to the Moon."
Answer: Doc was happy living in the Old West but returned to the future to collect his dog, Einstein, and he didn't want Marty to worry about him. He probably also wanted to make sure that Marty had made it safely back to his own time, to properly say goodbye, and make sure the DeLorean was never used again. He never indicated he would destroy the train, only the DeLorean. The hover conversion on the train would have been done in the Old West, not in the future.
I doubt he was able to make the train hover in the old west, whilst he could easily go to the future with it and do it there, like he did with the DeLorean. He did say he has been to the future with it, so it's logical to assume that's where he upgraded it.
Doc never says he went further into the future with the train or did the hover conversion there. If he could build a time-traveling locomotive in the 1880s, then he could create a hovering one, as he had the knowledge. Marty asks if he's going back to the future, and Doc says no because he's already been there. That could be interpreted a number of ways. It's a sci-fi movie, and there is a lot of suspension of disbelief employed here.
While the movie isn't explicit about when or where the Time Train was built, other sources do indicate its hoverconversion was done in the future. While Doc could invent a machine that was capable of time travel (the mechanics of which aren't really discussed), he had to travel to the future to convert the DeLorean and couldn't even fix the DeLorean in the past.
What 'other sources' indicate Doc travelled to the future for the hover conversion? Any fan speculation is invalid. I also don't get the argument. While Doc was unable to fix the DeLorean when Marty was in the Old West, he could, and did, in later years, build the time-travel train in the past. He could not otherwise have gone anywhere into the future to do anything. Time-travelling without the hover ability would be extremely difficult as a locomotive would be noticeable and require taking off and landing on empty train tracks. Doc would have to hide the locomotive while converting it. He would also have to know before time-travelling that the railroad tracks he took off on still existed in the future, as he could possibly arrive smashing into what became an urban development. This should be considered as both a deliberate plot hole and a plot device using "suspension of disbelief" solely intended to give the series a spectacular finale.
The comics reveal that Doc Brown traveled to 2017 in a prototype time machine and purchased materials which he brought back with him to the 1890s to use on the Time Train.
Question: Just before Doc shows his plan with the DeLorean and the train Marty checks the walkie-talkies and Doc confirms it that they work. How are they able to get the walkie-talkies to work in 1885? I'm thinking Doc invented something so Doc and Marty can communicate with each other with them.
Answer: Given Doc's scientific ability (and some suspension of disbelief) it would be easy enough to rig up a makeshift battery that would last long enough. Or indeed they've just got lucky and the walkie-talkies' batteries still have enough life in them. They're not mobile phones, they don't need masts or any infrastructure, they just connect directly to each other.
Like you said, walkie-talkies work independently of any infrastructure, which is what I think the question was more about. However, the battery was invented way before 1885 with the first lead acid rechargeable battery being invented in 1859 with pasted electrode batteries being invented in the 1880's. So it's less about Doc rigging up a battery and just using what's already available or charging the batteries it came with (if we are assuming the batteries ran out of power).
The best batteries they had in those days were crude, wet batteries made out of earthenware and filled with sulphuric acid. They were cumbersome, dangerous and didn't have a lot of voltage or low current. Hardly suitable for a walkie-talkie that needs at least 9 volts. But I suppose it's possible Doc had some charged self-made batteries sitting at home to keep them going.
Definitely not "crude", certainly not as advanced as today, but the lead acid battery is the same technology a lot of batteries use today. They even had electric vehicles prior to 1885. My point was Doc didn't have to invent technology that didn't exist (as opposed to what some say he would have to do to get an 80's camcorder to play on a 50's TV). They had rechargeable batteries back then so it wouldn't be a stretch that Doc could recharge the batteries he had.
Answer: 1955 Doc got him some new batteries ("Just in case, fresh batteries for your walkie talkie. Oh what about that floating device?") They only used them on the train so the batteries would still be charged. In regards to how they work, they don't rely on phone masts, satellites, WiFi etc as they send radio waves to each other and not to any sort of base station.
Question: When Doc and Marty hijack the train, they are both wearing masks. Marty zooms straight ahead as the train behind him goes off the tracks and explodes at the bottom of Shonash Ravine. When he comes back to 1985 there's a sign that says Eastwood Ravine. How could the people of Hill Valley know Clint Eastwood was on that train when he immediately took off and disappeared after defeating Buford Tannen?
Answer: In the novelization, the people of Hill Valley believed that 'Clint Eastwood' died trying to save the train from the bandits and was remembered as a hero.
Answer: Presumably, Doc, who remained behind in the 1880s, and Clara gave their version of the story about "Clint Eastwood" and influenced the naming of the ravine.
Question: Considering what happened with Old Biff and the Almanac in 2015, why did Doc not bother to ask Marty about the whereabouts of the DeLorean upon returning to 1985 in the train? Wouldn't he want to make sure it wouldn't fall into the wrong hands again? I mean he can see a bit of debris when he leans out the window, but that could have fallen off a passing scrap metal train or anything.
Answer: He's already been to the future, so it's possible (probable, even) that he spoke to Marty then and found out that the DeLorean had been destroyed in 1985.
Answer: Many people theorized that since Doc technically was the one that told Marty what time enter on the keypad as when they would arrive in 1985. It's plausible that Doc had planned the DeLorean to be destroyed by the train when they arrived. Remember the original plan was for Doc and Marty to go back together but then Clara showed up and complicated the plan (again). It's quite possible that when they arrived together in 1985 Doc would have warned Marty what was about to happen and they would exited the car long beforehand then to witness the DeLorean's destruction.
Answer: There was actually much debris (the entire car) around the track that Doc surveys as soon as he arrives with the time-travel train. He'd know better than anyone that it was the DeLorean, particularly as he planned his arrival for just a few minutes behind when Marty arrived back in 1985. Marty couldn't have done anything with the DeLorean in such a short amount of time.
Question: After deciding not to race Needles, Jennifer looks at the fax that she took from 2015 and sees that the words "YOU'RE FIRED!" were erased. Why didn't the name of the company also get erased?
Answer: The company would still be in the future, Marty wouldn't be working for it. His career as a musician would have taken off.
Answer: Because like Doc Brown, Clara has a thirst for adventure. An Old West lady being offered the chance to go back and forth in time. Also, to go to the final frontier, outer space. Besides traveling for them is like a vacation. They could settle in 1985 anytime they wanted.