Continuity mistake: When Marty confronts Biff in the alternate 1985 in the hot tub, the girls change positions. The blonde was on his left and the brunette was on his right. When they see Marty and scream, they move forward but there is no way they can switch that fast. (00:55:40)
Factual error: When Biff and Marty discuss the Almanac in the Alternate 1985, a magazine is visible. This is the March 1989 issue of "Mustang." (00:57:05)
Continuity mistake: When Biff, in the alternative 1985, presents the record book to Marty, he puts it in a safe behind a portrait, and then he closes it. Biff continues speaking and you can see that the portrait is slowly opening again. Cut to Marty, then back to Biff, and you can see that now the portrait is completely closed. (00:58:43)
Continuity mistake: After the roof scene in alternate 1985, the time circuits show the Nov. 12, 1955 readout before Doc enters it. (You can hear him still pressing the buttons afterwards). (00:59:00)
Audio problem: When Doc and Marty return to the year 1955, you hear the squealing sound of tyres braking heavily, but the DeLorean is flying. (01:02:25)
Audio problem: After Doc and Marty return to 1955 in an effort to steal the almanac back from Biff, they land the DeLorean. Doc says, "Here's some binoculars" then says "and" but watch his lips as he says "and", it just doesn't match. You could argue that it is a bad angle but even at the angle it's at, you get an OK view. (01:03:05)
Visible crew/equipment: If you look at the money case that Doc brings with him that has all the different types of money for each year, you will see where it says 1864 the reflection on the glass or plastic of what appears to be a tripod most likely for lighting. (01:03:47)
Factual error: When Marty enters the 1955 Hill Valley, one of the cars has a white licence plate with blue text and a sunset, which was not used until 1982. (01:04:54)
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: When Biff is trying to get Lorraine to go to the dance with him, (the bit when Lorraine is looking at her dress) you see the same extra walking past her about three times. (01:06:07)
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)
Audio problem: When old and young Biff listen to the end of the football game in the car, as the two are talking back and forth about how old Biff knew what the results would be, the sound of the announcer on the radio lowers and then suddenly disappears altogether... yet neither of them physically turn the radio down or off. The two are shown the whole time talking to each other and both their hands are away from the radio. (01:09:39)
Continuity mistake: In the part where Marty is trapped in Biff's garage, Biff's rear view mirror on his car is at the very top of his windshield. Later on when Marty is holding on to the car with the hover board the rear view mirror is in the middle of his windshield. The rear-view mirror was lowered about six inches or so. (01:10:12)
Revealing mistake: When the Doc of the future is in 1955 and sees the DeLorean, his hair is short (in fact you can see that the actor is wearing the wig that he wore for the 1955 Doc), but after a shot to Marty and back again, his hair is the same length as it was in 1985. (01:12:26)
Revealing mistake: When Marty, in the 1955 dance, looks at his father with his binoculars, you can see that the angle of the binoculars are really misplaced. Marty is looking at him at his far front, but the binoculars' image comes more from the floor. In fact, what the binoculars show is from the first film. (01:15:19)
Factual error: Marty is pursuing Biff at the high school as the other Marty pulls up with Lorraine in Doc's car. In the parking lot, the car closest to Biff is a brown 1957 Chevrolet. The front grill and styling are distinct and unique to the 1957 model year. In November 1955, it would be plausible to see a 56 Chevy in the lot, but a '57 is a bit early. (01:16:42)
Suggested correction: Watched this scene carefully and compared photos of the 1956 and 1957 Chevy to the car in question. It is almost certainly a 1956 Chevrolet 210. The grill could be mistaken for a 1957 in the dim light, but the real giveaway is on the hood: the '56 Chevy had a single, centred hood ornament (as seen on the car in this scene), while the '57 Chevy had a pair of "rocket" ornaments on either side of the centreline.
Continuity mistake: When Marty is in Mr. Strickland's office trying to take back the almanac, it shows a wide view of the office with two flags right next to each other. After cutting to a close up view of Marty they are apart, then Marty moves them together. (01:19:20)
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: 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 Doc flies the DeLorean up and the wheels get stuck to a banner string, the close-ups of Doc show a lit cockpit, but the shots from the outside show it's dark and one can't really see who's at the wheel. However, for a couple of seconds you get to see it's not Doc but a stunt double or a stiff dummy. (01:23:25)
