Continuity mistake: When Clara is about to leave Doc's workshop, the position of Doc's hand on the telescope alters each time we move from rear to front shot. (01:08:09)
Continuity mistake: At the bar Doc says that in the future people run for fun. When the guys playing poker laugh at him, the bartender magically appears next to them between shots. (01:17:43)
Continuity mistake: After the bartender prepares the wake-up juice, the two men by the table behind, plus the smoke coming out of the ashtray, disappear. When Marty pours the liquid the men reappear. (01:19:43)
Continuity mistake: When Doc drinks the 'wake up juice', he runs out and puts his head in the horse trough full of water. However, after a shot to Mad Dog Tannen, his shirt is mysteriously dry again. (01:20:05)
Continuity mistake: When Doc has just consumed the 'wake up juice' and runs out of the bar and dunks his head in the horse trough, Marty and the bartender come out after him. You can see that Doc is now soaked and a trail of water is on the ground behind him from a previous take of Marty dragging him back in the bar, which hasn't happened yet at this stage. Only really noticeable in the cropped version. (01:20:05)
Continuity mistake: After Clara pulls the emergency pull cord she jumps out of the train with her gloves on. From the immediate opposite angle her hands are bare. (01:26:04)
Continuity mistake: When Marty is shot by Buford, he is thrown off his feet and lands on his back. As he does, his poncho flips up, showing his shirt all the up to the middle of his chest. The stove door he is supposedly using as a bulletproof chestplate is conspicuously missing. (01:27:20)
Continuity mistake: When Doc and Marty are chasing the train, first their shadow is on the left of them, then in the next shot it's on the right. (01:30:40)
Continuity mistake: When Doc and Marty are chasing the train on horseback, Doc gets on the train first and his horse pulls forward. Then when the camera shows Marty on his horse, another horse can be seen in front of him. When Marty jumps on the train, his horse falls back. But in the next shot you can still see the horse as it moves off camera. (01:30:55)
Continuity mistake: When Doc and Marty get on the train at the end, Marty has some trouble getting on, and note that his hat falls off in the sequence, but in the next shot when Doc and Marty fall the hat is back on. (01:31:15)
Continuity mistake: When Clara first sees the train and starts after it on horseback, it is on her right side. She is at the top of a hill and starts down after the train. In the next shot shown from the front of the train you see the horse appear so the train is on Clara's left. (01:34:09)
Continuity mistake: When the train hits 70 mph the chimney explodes to pieces. When the bar that Clara holds onto breaks the chimney reappears. (01:39:53)
Continuity mistake: After the train crashes against the "Tracks end" sign, the editing is all wrong: Marty is inside the car covering his head with the hover board. Half a second later he has magically moved outside the car, dangling and holding the hover board. Then we see Clara upside down, and back to Marty back inside, removing the hover board from his head after the crash. then he dangles outside with the hover board. So the first shot of him dangling shouldn't have been there. (01:40:42)
Continuity mistake: When the railroad is about to end, Marty puts on his hat and there's a POV shot where we see the train passing by some abandoned tracks on the grass to the left. Then a wide angle shows some explosions going on and the train passing by the same place again. (01:41:37)
Continuity mistake: In the scene where Marty is driving the black Toyota pickup at the end of the movie, the truck's registration plate is missing - it can be seen when the truck is in the garage at the start of the film. Also the driver's door quarter light (vent window) is open. When we see the inside of the door it is closed. (01:41:45)
Continuity mistake: When the train is coming and is about to run over the DeLorean, the shadow of the train on the wall shows that it is only the locomotive. When the camera changes view, it is a train with freight carriages. (01:43:00)
Continuity mistake: In the last fifteen minutes of the film Marty wears his Wild West clothes, including his brown woolen poncho. The front of the poncho is unmarked, completely intact. Shouldn't it have a bullet hole in it? (01:43:50)
Continuity mistake: When Marty returns to 1985, he goes to his house and gets in his Toyota pick-up. Look closely behind his head when he first gets in the truck, there is no driver-side head rest. But when he picks up Jennifer, when they pull up to the stop sign the head rest is there. (01:45:00)
Continuity mistake: When the movie is about to end, Marty picks up Doc's photo. From the front shot he is grabbing it by the middle, but in the opposite angle he holds it by the lower end. (01:48:40)
Continuity mistake: At the very end Doc comes back to 1985 in the train. When the train is slowing down they cut to Marty and Jennifer on the ground and the shadow of the train is not moving. But when they go back to the train it is still slowing down. (01:48:55)
Answer: Someone would go into his barn and do what? See a sign that says time machine and believe it and then use it? Seems highly unlikely.
lionhead