Continuity mistake: When Marty is standing over his father's bed in 1955, Marty puts the headphones on George and then puts the tape in the cassette player. If you notice the hairdryer is on the left side of the belt and is touching his left arm, but when they cut to Marty holding the tape player out in front of him the hairdryer is on the right side. (01:02:10)
Continuity mistake: In one shot of Einstein strapped in the DeLorean, if you look closely in between the steering wheel, the yellow time circuits on the bottom read the month as "10" rather than "Oct." And the red and green time circuits read "11" instead of "Nov." (00:19:20)
Continuity mistake: In 1955, when Doctor Brown is watching the video of himself, he sees himself saying that the Libyans are coming. You can hear a significant pause between "They found me" and "I don't know how but they found me." But in the beginning of the film he says the entire phrase without any pauses. (00:28:45 - 01:08:10)
Continuity mistake: Beginning of film. When Marty arrives at Twin Pines as the Doc requested he cruises up alongside Einstein on his skateboard, saying "Where's the doc, boy?" There's a cut to the truck opening, then back to Marty, and for some strange reason the yellow wheels on his skateboard have turned pink, but the reflection on the wet car park is still yellow. It cuts back to the DeLorean coming out of the truck then back to Marty, and his wheels are yellow again. This doesn't happen in the VHS version. (00:17:40)
Continuity mistake: When the lightning bolt hits the clock tower in 1955 and sends the DeLorean back to 1985, Doc Brown gets up and looks at the clock tower. What happened to that awful lightning storm of only a few seconds earlier? Not even a trace of wind is present in Doc's hair. (01:36:55)
Continuity mistake: When George goes into the cafe to tell Lorraine he is her density/destiny, the people sitting at the bar keep changing with different shots. Best example is just after George refers to his "density" - in the background there's a brunette in a blue jumper at the bar. A blonde woman and a short-haired guy then sit on her left, but then disappear in the shot of Marty sitting at the bar - on the brunette's left there's now another brunette in a pink jumper with a different guy. The brunette's got shorter hair too. In the very next shot the blonde's back with no sign of Marty. (01:02:10)
Continuity mistake: At the Twin Pines mall during the chase scene with the Libyans, there is one shot where you get a great look at the driver as he's trying to start the engine. Later on you get another look at the driver as the van is moving and it's a totally different person. (00:29:52)
Continuity mistake: As Marty drives the DeLorean towards the clock tower, if you look carefully you can see that he drives past the 'Bluebird Motel' billboard at least 3 times (which is where he started from) and drives past that small building with the slanted grey roof in the square about 4 times.
Continuity mistake: After Marty has been thrown into the bookshelf after the amp explodes, he is lying on the floor with his left leg bent at the knee. In the very next shot however, he has not moved but both legs are straightened and on top of each other. (00:04:05)
Continuity mistake: 1955 Skateboard Chase Scene around Town square. After Marty falls over the couple, a shot of Biff's car shows all the passengers standing up, but in the very next frame everyone is sat down. Also, that is not Biff driving. (01:04:20)
Continuity mistake: At the beginning of the movie after Biff leaves the McFly home. There is a scene where Marty and George are talking. In one shot George has three pens in his pocket, a few seconds later he has two. (00:14:14)
Continuity mistake: While Doc is waiting for Marty to get back from the dance, he looks at the watch on his left hand, his pocket watch, and the watch on his right hand. When he looks at the watch on his right hand, he is wearing it on the inside of his wrist. Then, as he is running around the car, he has no watch on his right wrist at all. Moments later, as he is pointing down the street, it is on the outside of his right wrist. When they are checking the alarm clock, he holds it in front of the alarm clock to check the time, and the watch is still on the outside of his right wrist. (01:31:15 - 01:32:30)
Continuity mistake: At the dance, when Marty is parked with Lorraine, Biff reaches into the car and grabs the front of Marty's shirt/tie, but in the next exterior shot, Biff now has got hold of the back of Marty's suit. (01:20:10)
Continuity mistake: Lorraine throws Joey's cake on the table and a close-up shows nothing next to the tray. When the angle changes, a Pepsi can has appeared right by the middle of it.
Continuity mistake: When Marty arrives in 1955, he lands on Peabody's farm and rams through the pine tree he then hits a scarecrow which flies over the top of his car. Then as they show it from the inside the scarecrow slams into the windshield - but how can it slam into his windshield if it is already over the car? (00:31:30)
Continuity mistake: When Marty gets out of the DeLorean to look at the "Lyons Estates" markers it is supposed to be a little past sunrise. The shadows should be very long, but all of the shadows are small. The scene must have been shot much closer to noon. (00:32:40)
Continuity mistake: In the scene after Marty returns to 1985 he jumps out of the DeLorean to verify he's back and then jumps back in the car to go save Doc at the mall. In the shot where he's putting the car in gear, you can read part of the yellow "Last Time Departed" display on the time circuits as "1985, 1:20AM", and in the shot where he's trying to start the car, you can read "Oct". It should read "November 12, 1955, 10:04PM" since that was the time he just left. On top of all that, the display appears to relate to when Einstein traveled a minute into the future (you can see when Doc shows Marty the time circuits after he lets Einstein out that the "Last Time Departed" is "October 26, 1985, 1:20AM"), not when Marty traveled back to 1955 (October 26, 1985, 1:35AM). You could argue that the "Last Time Departed" display is not working properly, but Doc uses Marty's last time departed (October 26, 1985, 1:35AM) to set Marty's destination time when he's returning to 1985. (01:42:40)
Continuity mistake: When Biff chases Marty out of the cafe in 1955 and Marty 'makes' the skateboard, there is an odd shot of a tree. When Biff's car drives through the grass, the big tree in the shot is shaking violently, yet all the trees are completely still during the chase before and after this shot. During this entire scene, differences regarding varying degrees of windy then calm, wet vs dry pavement and variations in shadows cast are numerous. (01:06:30)
Continuity mistake: In the chase scene with Marty and the Libyans, Marty is driving away from them. He changes into second gear but in the next shot he shifts into second gear again without changing back. (00:30:15 - 00:31:10)
Continuity mistake: When Biff's car slams into the manure truck, in the first shot the side of the truck is adjacent to the car's back passenger door, but in the next overhead shot the side of the truck is adjacent to the front windshield. (01:07:20)
Chosen answer: I think that is *exactly* what he is thinking. He realizes that by standing up to Biff, George may have irrevocably changed his personal future, and therefore affected Marty's future as well. This is exactly the sort of thing Doc was so eager to prevent by refusing to hear any information about the future.
Phil C.