1. There should be an infinite number of Martys coming back to the future from 1955.
Towards the end of the film, Marty sees himself travel to the past, so the Marty that he sees needs to reappear…and thus forth. Why doesn’t the second Marty come back from 1955? On that note, if these Martys keep going back, only one of them can harness the lightning bolt, forcing the others to stay in 1955.
2. Doc should already know he is going to die from the beginning.
Doc reads the note Marty wrote for him (for whatever reason), yet he still hold the testing of the Delorean at the Twin Pines mall, where he knows the terrorists will arrive. How does Doc know that this will be the exact moment Marty will travel back to 1955? Also, if Doc knows that his invention of time travel works, why does he need to test it in the first place?
3. Marty is technically named after himself.
Marty’s mother meets Marty and comes to like the name Marty enough to name Marty Marty because she met the same Marty she named Marty.
4. Marty wrote Johnny B. Goode.
Marty played the Chuck Berry song in 1955 before Chuck Berry wrote it himself. Therefore, Chuck Berry plagiarized Marty’s work which was actually Chuck Berry's. Marvin Berry calls Chuck to tell him of the sound he is looking for.
5. Goldie Wilson would not have been mayor without Marty’s help.
If Marty did not go back in time, Goldie would not have gotten the idea to be mayor.
6. If parts of Marty’s timeline are erasing, how does he remember them?
Since his brother and sister are ceasing to exist, shouldn’t they also cease to exist from his memory?
7. The clocktower should have never stopped working.
By directing the lightning away from the clocktower, the clocktower was never hit and should still be working in 1985.
8. Once returning to the new 1985, Marty has no recollection of his childhood.
His entire life is different and he barely even recognizes his family. All of the memories he has belong to the previous timeline. What would growing up in that life have been like?
9. If Doc were to die, Marty would be stuck in 1955 forever.
If Doc were to fall off the clocktower or get struck by lighting, the Delorean would instantly vanish because Doc never invented it, thus stranding Marty in 1955.
10. The series should end here.
By leaving with Doc to go to 2015, Marty has removed himself from the world for 30 years. Where did the Marty that aged and had a family come from?
