Avengers: Endgame - 10 Secrets We Just Learned From The Writers At Comic-Con
8. That Back To The Future Jab Was A Direct Quote
We already knew that the team behind Endgame consulted with physicists to help them map out the movie's depiction of time travel, but we now have a little bit more of an insight into the firm stance they took on the matter.
Where a lot of popular time travel tales abide by the "Back to the Future" rules - i.e. if you shoot your past self, your present self will disappear - Endgame instead opted to go with alternate timelines and the multiverse, so when present Nebula kills her past self inside the wrecked Avengers HQ, she stays put.
And because it wanted to point out that this version of time travel was not like the one seen in the beloved sci-fi classic, Endgame even featured a line that straight-up told audiences as much: when Scott Lang asks if Back to the Future is "bull****".
As revealed at Markus and McFeely's panel, that remark was a direct quote from one of the experts the filmmakers spoke with, who clearly isn't the biggest fan of Back to the Future's scientific accuracy.