Revealing mistake: During the hoverboard chase in 2015 between Griff and his gang and Marty, you can plainly see the wires holding the gang up on their hoverboards in the wide shots as well as on the Jeep Wrangler before it lands in front of Marty.
Continuity mistake: At the start, when Marty and Jennifer kiss, Marty turns toward his parents standing at the door. The screen door has three lower sections, and the house numbers are black. When Doc says, "Where we're going we don't need roads," it then cuts to Biff rushing out the door. Now, in this shot the changes include a screen door with four lower sections, stone wall differs, the house numbers are bright white, and a light fixture directly over the house numbers. (00:01:05 - 00:02:20)
Continuity mistake: When Lorraine, Biff and Marty are in the hotel in the alternate present, after Biff has said "...and all three of them?", Lorraine puts her drink down on the table with her left hand. In the very next shot, she is holding the drink in the other hand.
Continuity mistake: If you look at the destination keypad, you will see that the PM is over the AM. In the first "Back to the Future" film (1985), the AM is over the PM.
Continuity mistake: In the original BTTF the photo used to determine if Marty would exist in 1985 (the one with his brother and sister) is a wallet size photo. Yet when Marty in BTTF II (with the leather jacket) sees the other Marty from BTTF look at that photo and rush back to the dance, it's a regular size photo. (01:22:27)
Revealing mistake: When Griff and his gang are chasing Marty on the hoverboards in a few shots after Marty is hanging off the back of the Jeep, when the shot shows the gang catching up, the Jeep goes through some wet places in the street, showing the camera car's tire tracks. They're not the Jeep's because the tire tracks are double-wheeled and the Jeep was not turning in that shot. (00:19:22)
Continuity mistake: The garage where Marty's truck is parked is very different in the opening scene of BTTF II than in BTTF I. The gardening tools on the wall to the left were different, and the brown wall siding in the back of the garage was not there in Part I. (00:00:38)
Continuity mistake: At the start of this film (and the end of the prior film), Marty and Jennifer talk with Doc who has just returned from the future to retrieve them. A shot looks over the rear half of the DeLorean at Marty and Jenn and we see the street behind them. Ignoring that Jennifer is now played by a different actress, there is a tree missing behind her, as is the truck with a camper-shell that was two driveways back. Parked in the street is a VW bus where a Pontiac Firebird was. Marty has also gained a wristwatch not present in the same scene in the earlier film. (00:01:40)
Continuity mistake: When Marty is being chased by Griff's hover board gang, Marty grabs rope from a car. Just after, he has to avoid an oncoming car. One second he's holding the rope, the very next shot as he goes over the bonnet, the rope's gone. (00:19:38)
Continuity mistake: When Old Biff drives into the garage with Young Biff in the passenger seat, Young Biff (body double) is not wearing a belt, but the belt reappears when they exit the car and Old Biff places the Sports Almanac in Young Biff's back pocket. Also, the Levi's small red tab is now missing from that pocket. (01:07:55 - 01:10:05)
Continuity mistake: When Doc tells Marty, "Don't do anything, don't interact with anyone, and try not to look at anything," note Doc's red shirt design. Then it cuts to a shot of Marty as he says, "I don't get it, I thought you said this had something to do with my kids." The next shot facing Doc, as he says, "Look what happens to your son," his red shirt's design has changed, though it's the same style shirt. The same thing occurs with Doc's yellow shirt with the train design, but it's more subtle. (00:09:25)
Continuity mistake: Marty's new Toyota truck in the garage at the end of Back to the Future and beginning of Back to the Future Part II has different front license plates. In the first movie it's 2EZP916 then it's changed to 2BAK860.
Continuity mistake: When Marty and Doc find Biff's car, Marty is not present in the DeLorean, but he appears in the next shot. (01:29:54)
Visible crew/equipment: When Marty realises that the almanac is not inside the dust jacket, a set light can be seen on the far right side of the screen. It can also be seen when he realises where Biff is. (01:21:08 - 01:21:45)
Continuity mistake: When the police car arrives in Hilldale, there are no door handles on the car, but in the next shot, some appear. (00:27:16)
Continuity mistake: When Marty hides in Biff's car as he walks over to it after leaving the auto shop, the left visor on the car is raised, but in the next shot, it is lowered. (01:05:53)
Continuity mistake: We see Marty putting on his right Nike boot but not his left. The camera cuts from his feet to his face saying "power laces, all right" then back to his feet, now both boots are on. (00:07:45)
Continuity mistake: At the end of the first film when Marty leaves the garage to greet Jennifer, he does not have a watch on throughout the whole scene. In the identical scene at the beginning of this film, Marty is wearing a black watch.
Continuity mistake: At the beginning, when Marty is examining his truck in the garage, the left side of his shirt is tucked-in in the front, but in the first film, Marty's left shirt tail was hanging out. (00:00:36)
Continuity mistake: At the start, the DeLorean hits the left dustbin and comes to a halt. At the other side of the street, there is only one car parking near to a house. From another angle there's a different red car parking on the other side of the street, and the tree that stood between both houses has gone. (00:01:15)
Answer: Yep, and there is, but they're both elsewhere. Doc's been committed to an asylum somewhere. When Marty first meets the alternate Biff, Biff tells him that he's supposed to be in Switzerland at boarding school - that's where the alternate Marty is.
Tailkinker ★
Wouldn't someone probably see Doc and report that he escaped from the asylum?
Maybe, but no way to be sure, and they're not around long enough for that to be an issue anyway.
Jon Sandys ★