In BTTF 2 after Marty and Doc come back from the future (to 1985) where Biff has already gone to 1955 and changed 1985, they stop off at what they think is Jennifer's house and leave her on the porch swing at night. Of course, as that timeline is now changed to Biff's Paradise, that is not her house presumably.

At this point the remaining story of BTTF 2-3 progresses. BTTF 3 ends with Marty coming back to 1985 and arriving at Jennifer's porch where she is still in the same place, waiting to be awoken.

My confusion is this: She was left in the timeline while it changed from Biff's Paradise(BsP) to the "regular" timeline. Considering if the movie uses either the distinct multiverse theory, or one in which there is a single timeline which can be and does alter to accommodate changes within itself, there must be two possibilities:

Multiverse- Jennifer is left on the porch in the BsP timeline and when Marty and Doc leave to change the past in order to return back to their "normal" timeline, she is left in the BsP timeline and should NOT be in the "normal" timeline, as she was taken OUT of it along with them WITHOUT being brought back to the "normal" timeline by the DeLorean. If you can imagine two lines where line 1 is the "regular" timeline and line 2 is BsP timeline. If Jen was pulled from L1 to the future and set into L2, when Marty and Doc go back to change the past and return to 1985 it is the L1 1985 where Jen should not be in.

Single, changing timeline- Jennifer is left on the porch in BsP, but when the past is changed, her and everything in that timeline are changed back to the "normal" timeline. However, Marty and Doc were never in the "regular" timeline to put her on that porch in the first place. It is my opinion that if this is the movie's preferred time-theory, she should be going about her life as everyone else is after the timeline changes.

I know this whole topic is very confusing and hard to straighten out, but my final question is which theory seems to fit best, or is there another one to better address Jen's fate?

  • I'm not sure what you mean about Marty and Doc never being in the "regular timeline" to put her back on the porch, or "she should be going about her life as everyone else is"... if there's one timeline, putting her back on the porch was them putting her back on her porch, and she DID go back to her life as everyone else did, just having been woken up from her nap, and with memories of being in the future (since she still travelled there no matter what changed). Commented Aug 5, 2016 at 14:59
  • @starpilotsix By the single changing timeline theory, time changes to adapt to the changes in the past made by Marty and Doc. All three characters left regular 1985 and Marty didnt come back until the end of BTTF3 when he rode in on the train tracks. He then goes to Jen's house where she is on the porch. But he was not around in that time to put here there so she SHOULD be going about her business, not still sleeping on the porch as if she had been put there like in BsP timeline. Commented Aug 5, 2016 at 15:13
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    But... he WAS around in that time. They time travelled to 1985, dropped her off. You're still viewing it as though it was an ALTERNATE 1985. In the single timeline theory, 1985 is 1985. If you dropped her off there and went to 1955 and altered history, you still had just been to 1985 and anything you left there would be changed if required by your actions. But their actions just restored the original events, so Jennifer didn't need to be altered. Commented Aug 5, 2016 at 15:16
  • @starpilotsix So then if you were watching the events of regular 1985 uncut and following the single-verse you would see Marty, Doc, and Jen fly off down the street to the future, come back from the future, put her on the porch, then....go off and do what? So many inconsistencies!!! Lol. I see what you're saying, the universe change around her, herself included, she just remained there because it fit the universe? Commented Aug 5, 2016 at 15:22
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    I think there's sort of the concept of changes taking a certain amount of time to "catch up". He travelled back to 1955, made changes, then immediately came home. From the objective time-traveller's perspective, the new timeline hadn't "caught up" to him, so he returned to an unchanged 2015. Then Doc and Marty returned to 1985, and it had caught up that far, and maybe a few 'objective' minutes later, future Biff would start to witness time change around him (time travellers seemingly being protected by at least a little bit of a bubble). Commented Aug 5, 2016 at 17:22

3 Answers 3


The single changing timeline seems to be the one the writers imagined, and they also imagined that when time traveler A is in one era and time traveler B in earlier era changes history, the world will transform around time traveler A via the ripple effect. BTTF writers Bob Gale and Robert Zemeckis wrote up an official BTTF FAQ where they talked about the related question of why old Biff returned to the same 2015 that Marty, Doc, and Jennifer were in, and they mentioned that 2015 transformed into 2015-A around M&D&J in the same way that 1985-A transformed back to regular 1985 around Jennifer on the porch:

1.9: When Doc and Marty are in 1955-A, Doc says they can't return to the future to stop Biff from stealing the DeLorean, because it would be the wrong future. But if that's true, how did Old Biff manage to get back to the same future that he left? Shouldn't he have come back to a different future?

A: As should be clear from the answer to the previous question, we believe Old Biff DID indeed return to a different future — a "2015-A," which would have transformed around Marty, Doc, Jennifer and Einstein (just as Doc explains how 1985-A would change into 1985 and instantly transform around Jennifer and Einstein). This would happen AFTER Old Biff returned with the DeLorean. For this reason, we made sure that Doc had caught Jennifer and exited the McFly Townhouse before Old Biff returned. Thus, by the time Marty and Doc are carrying Jennifer back to the DeLorean, there COULD be other residents in that townhouse — or perhaps the McFlys still live there. It is just as believable that the physicality of the neighborhood did NOT change as it is to believe that it did — so we didn't change it. We decided not to make anything of this idea because this is one of those difficult time travel concepts that general audiences have a real hard time understanding. (Try explaining this stuff to your mother and you'll see what we mean.) A detailed explanation of it would have slowed down the story, and most of the audience doesn't ever think about it. That's why we made certain things ambiguous and left various things open for interpretation in hopes that the possibility of at least one or two explanations would be better than a "definitive" explanation that you could find holes in. Let's face it, time travel is fantasy, so there's no way to "prove" anything. As filmmakers, we try to create a set of rule for our stories and stick by them, and stay consistent within the little "universe" that we've created.

For some speculations about what this implies about the "rules" of time travel in BTTF, see my answers here and here.

As for your comment However, Marty and Doc were never in the "regular" timeline to put her on that porch in the first place, one way I might think of this would be to imagine there was a security camera on the street aimed at Jennifer's porch the whole night; then in the final timeline at the end of part III, what would the tape show had happened that night? I think this is getting into issues Gale and Zemeckis never really considered, but if you go with the theory I suggested in the second of the two answers I linked above, different timelines appear in a sequence in "meta-time", and whenever a time traveler materializes on a given date, they always retain the memories of the "first" version of the timeline where they made that trip through time (see my comments in that answer about their memories and appearances on arrival being 'burned in' to all subsequent versions of the timeline). So, on Saturday Oct 26 1985 at 9 PM (the date and time they arrived in 1985-A in part II according to this chronology), there will always be a DeLorean appearing in the sky over Hill Valley, containing a version of Doc and Marty (and sleeping Jennifer) who remember having just had the adventures in 2015 that we saw in part II. This will even be true in the final timeline, where instead of returning to a horrific 1985-A they return to the "normal" 1985 we see at the end of part III.

I would also speculate that the "Self-Preservation Instinct of the Space-Time Continuum" which Gale and Zemeckis discuss in question 1.19 of the FAQ (and which I discuss in that earlier answer) causes Marty and Doc to still leave Jennifer on the porch in this different sequence where they return to a normal 1985 rather than 1985-A (since after all, when they left her there in 1985-A they hadn't yet realized the timeline had been altered), so that the security camera tape would show her ending up on the porch naturally and then waking up the next morning when Marty arrives in his Western outfit. But as an alternative possibility, I suppose the tape might just show her appearing on the porch via the ripple effect.

  • But isn't that exactly what Doc was saying, that they COULDNT go forward to stop Biff because it would be the BsP future where he never had to steal the Delorean in the first place? I always took Biff''s return to the "regular" 2015 as a result of all the movies "fixing" the timeline. We see Biff return because his efforts were in vain due to the conclusion of BTTF2. So, I get that the universe changed around people, but I'm asking HOW Jen was able to end up on the porch? If the universe changed, shouldn't she also have? Commented Aug 5, 2016 at 15:40
  • "We see Biff return because his efforts were in vain due to the conclusion of BTTF2." - But the FAQ from Gale and Zemeckis contradicts that theory, it says Biff did return to 2015-A, and regular 2015 changed to 2015-A around Marty/Doc/Jennifer. They even suggested it's possible the 47-year-old Marty and Jennifer would no longer have been living in the townhouse at that moment, but they didn't want to make any visible changes to the "physicality of the neighborhood" (i.e. what we see of it onscreen) to avoid confusing the audience.
    – Hypnosifl
    Commented Aug 5, 2016 at 15:56
  • (continued) "So, I get that the universe changed around people, but I'm asking HOW Jen was able to end up on the porch? If the universe changed, shouldn't she also have?" - See above, I think you are misunderstanding something about the phrase "changed around". It literally seems to mean the time traveler stays exactly the same while the world around them transforms via the ripple effect, since that's exactly what Gale and Zemeckis say happened when 2015 transformed to 2015-A around Marty/Doc/Jennifer.
    – Hypnosifl
    Commented Aug 5, 2016 at 15:57
  • So because they time traveled they are free from the changes of the universe around them? Does that not contradict the events of the first movie where marty's hand fades away? Commented Aug 5, 2016 at 16:10
  • I'd speculate that they are free from having their memories altered, but there is some special rule that kicks in when they shouldn't exist at all in the new timeline, and that causes them to fade away if they don't successfully change things back to ensure their existence quickly enough.
    – Hypnosifl
    Commented Aug 5, 2016 at 16:16

There is a single changing timeline

I tried to illustrate why I think there must be a single changing timeline.

step 1

step 2

step 3

step 4

To sum it up, if alternate timelines persist in the BTTF universe, I can't think of any reason why Doc and Marty would have traveled to BsP 1985 rather than to the original 1985 from 2015.

So your question remains, how could Jennifer have gotten back to the original timeline (since she was never dropped off in the original timeline)?

My response is:

When the BsP timeline converted back to the original timeline, Jennifer was transferred to the "nearest match" location in the original timeline.

You can think of it as "where would Doc and Marty have dropped Jennifer off if they had dropped her off in the original timeline?"

That seems to be how timeline reversion works in the BTTF universe.

  • Thanks a lot for making these helpful charts! So this theory is that the universe "fixes" mistakes or tends towards order, if you will. Not bad, I like this idea, though it does seem somewhat mystical in my opinion. lol I appreciate the discussion though! Commented Aug 5, 2016 at 15:35
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    Yes, the universe does seem to merge realities in a mystical/magical way. There are lot of examples of this in the film, like when the newspaper article changes "Emmett Brown Committed" to "Emmett Brown Commended", with the poses in the two photographs being nearly identical! The BTTF universe has a good sense of poetic justice. Commented Aug 5, 2016 at 15:58
  • On the same tack, how did the matchbook Marty obtained from Biff's Pleasure Palace turn into one saying "Biff's Auto Detailing"? Auto-Detailing-Biff at the beginning of Part II tried to show Marty the matchbooks he'd had printed, but Marty was already in the DeLorean, and never saw them. Shouldn't the Pleasure Palace matchbook have disappeared from Marty's hand altogether rather than changed?
    – Wallnut
    Commented Oct 21, 2016 at 12:54

The reason Jennifer was still on the porch at the end of Part III was because when 1985A rippled back into the normal timeline, everything else changed and Jennifer remained on the porch because she wasn't native to Biff's world. Like Doc said, the world literally transformed around her. Had Jennifer been awake, she would've literally saw the bars on the window spontaneous ly disappear, the streets magically become cleaner, and she would also see Biff's hotel shimmer back into the clock tower while everyone who actually lives in Biff's world wouldn't notice.

  • Nice. So could you address which of the versions of time travel mentioned in the question this is (or if it is an entirely different one)?
    – Adamant
    Commented Aug 16, 2016 at 8:22

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