Marty McFly goes back in time to visit his mum-to-be and finds her watching an episode of The Honeymooners. The date is given as November 5, 1955 and yet the episode of the show - The Man From Space - was not screened until December 31, 1955.
Doc sends Einstein (the dog) one minute into the future. The clock around his neck and the one that Doc has match up exactly. So Einstein should be gone 60 seconds, but he is actually gone for one minute and 28 seconds.
In the scene where Marty is being chased by the Libyans, a couple of times they cut away to show the instrumentation in the car. They actually cut away twice, I believe. But if you look at the reading of the first and second times, you'll notice that the first shot of it is actually more miles than the second time they show it.
When Doc sends Einstein into the future, he never sets the time circuits.
Doc Brown is explaining to Marty that you can go to any time you want by entering in the date in the console. Doc says you could go back and see the birth of Christ and types in Dec 25, 0000. Christ's birth is only celebrated on the 25th of December. No one knows the exact date (but it's believed to be around June). Also, the year 0AD did not exist. The Gregorian calendar started with 1 and not zero. The year before Christ's birth was 1BC and the next year was 1AD.
The electric guitar Marty plays at the "Enchantment Under the Sea Dance" is a Gibson ES335. This guitar model debuted between 1957 and 1958 yet he's supposedly playing it in 1955. It would have been more accurate to have him using a Fender Telecaster (1950) or Stratocaster (1954).
When Marty encounters Doc Brown for the first time in '55, after he tells Brown that Ronald Reagan is the president in the future, Brown makes a snide comment about Jane Wyman being First Lady. In fact, Ronald Reagan married Nancy Davis in '52.
In an early scene featuring Marty and his girlfriend they are sitting on a bench when a car with two loudspeakers passes in the background, one pointing forward and one pointing backward. Another angle appears of them sitting on the bench but the speaker pointing backwards mysteriously has disappeared.
At the end of the movie when Marty goes back to the future, we all see the license plate fall off, but if time travel causes the license plate to fall off, then it should've fallen off when Marty went to 1955.
Just how long must it take for a Delorean to hit 88 mph? Now I know that movie time operates under its own physics, but, in both the coming and going to and from 1955, the 0 to 88 mph run is Yugo-esque (or worse!) Granted the Delorean is/was no Ferrari, but still....
What are the odds that the bolt of lightning would make contact with the clock tower at precisely the moment the Delorean's hook hits the crosswire? Especially if the 0 - 88 mph elapsed time is so leisurely....
Doc uses a bike in 1955, and finds his other self and covered Delorean. If you look at the same scene in the 'Back to the Future' carefully, you actually find Doc on the bike passing behind the Delorean while Marty and Doc of '55 was talking.
In the scene where Marty avoids Griff and his thugs by jumping in the water off his hover board, his hair gets wet. After his coat dries his hair he rubs his hand through it. It gets all messy and crazy and uncombed. The very next shot shows him talking to the girls with perfectly combed hair.
When Marty's alcoholic mother gets slapped to the floor she isn't wearing shoes, when she is shown lying on the floor she is wearing pink pumps. Or is it the other way around?
When the Doc gets hit by lightning and goes back in time, he's not going 88mph, which Marty had to do in the first movie.
If Old Biff changed his past and went back to 2025, he goes back to HIS future, not the bad future, but Doc later tells Marty that if he were to go to the future to stop Biff from taking the almanac, he'd go to the bad future, so Old Biff technically shouldn't have been able to return to his future.
If Doc saw his tomb and sent Marty to 1885 he shouldn't be surprised to see him.
Why couldn't they just transfer the fuel out of the other Delorean that Doc came back in? There is the one that 1985 Marty came in from 1955, and there is the one that 1985 Doc came in from 1955. The one Doc came in was probably intact enough to be used to transfer fuel. [The Indian's arrow had torn the fuel line].
While at the dance Marty is showing off at the shooting gallery. After shooting all the targets he twirls the gun and hands it back to the booth operator with the barrel in his right hand. Very clearly the next frame shows the gun in his left hand.