Plot hole: Christopher Columbus speaks Italian while the Huns supposedly speak their native language. Shouldn't Octavius and his Romans speak Latin? (00:34:50)
Plot hole: How could the police miss finding Cybil in the trunk of Michael Zane's car when it was in an impound lot? They would have definitely searched the car if he was found in violation of a federal offence (for carrying the weapons). Even if they didn't do a search, they would certainly have heard the sounds that Cybil would have made from being locked in the trunk.
Plot hole: When Elizabeth is interviewing Victoria for the first time, she mentions that Victoria had sent her an application, therefore her name had to have been on it. However, Maggie Evans didn't change her name to Victoria Winters until she was on the train en route to Collinwood for the interview, therefore Elizabeth would have been expecting Maggie Evans, not Victoria Winters.
Plot hole: When Renee Russo was reviewing the tape showing the room with the painting to see who stole the painting, and the tape was blank because the heat generated from the suitcase hidden under the bench, why didn't she just back up the tape completely to see who put the suitcase there in the first place? (00:28:30)
Plot hole: Delores is walking into the murder scene at the beginning of the movie just as Ernie is shot. Later, while she is being questioned, she tells the two detectives what the thugs said and did, yet, she was not eavesdropping or looking through the door.
Plot hole: Cutting plastic explosive and disguising it as chewing gum wouldn't hide the smell from bomb sniffing dogs.
Plot hole: When Fluffy saves Chloe she calls out 'thank you Fluffy'. Cruella never told her the dog's name so how did she know it?
Plot hole: Johnny's dad jumps in his truck and gets to Johnny in moments. That same journey was shown to be an overnight bus journey for everyone else.
Plot hole: If Old Biff changed his past and went back to 2015, 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 at all.
Plot hole: In the final tournament when Happy is stuck in the rough, he swings five times. Assuming he hit his drive into the rough and hit an AMAZING shot from the edge of the water into the hole, he still could do no better than a seven on the hole. Happy only lost one stroke on the hole. (01:16:50)
Plot hole: The Toymaker throws that toy bird at the hippie version of himself. The toy goes through him because he is a hologram. Later, he pushes the soldier version of himself at the screen making it crack. How could he if the three others are holograms?
Plot hole: Why was $100,000,000 worth of heroin sitting in the police vault all this time before the bad guys stole it? Wouldn't the DEA have taken possession of the drugs long before that?
Plot hole: When Jake first meets Reggie, he tells Reggie that the Great Turkey told him everything about him. Later in the movie, when Reggie goes back in time and introduces himself as the Great Turkey to a young Jake, he only tells Jake to find the "Pardoned Turkey" but never said that the pardoned turkey's name was Reggie, so there's no way the adult Jake would know Reggie's name when they first meet.
Plot hole: When Moana first meets Muai, she opens her necklace to tell him he will restore the heart. Muai sees the heart but doesn't get scared until he sees it again on the boat. He should have been scared the first time.
Plot hole: In the scene when the robbers first enter the house, Kevin goes to hide in the shower. It looks like there is only one way out of the shower. How can Kevin possibly get out of the shower, let alone the bathroom, without getting wet after he turns it on?
Plot hole: When Terry gets back to her computer, after escaping from the spies and cops, the time is after 3pm New York time. If Jack actually is in Russia or Eastern Europe, wouldn't he have already gone to, and been killed at, that 5pm meeting?
Suggested correction: The effects of the past being altered may not have happened immediately. It is possible that it took time for the timelines to adjust to the changes of events, meaning enough time would have passed to change 1985 when they return, but not enough time could have passed to change 2015. By the time Doc says if they went back to 2015 they would be going to an alternate future, some time has passed, so the effects of the past being altered and taking ahold in 2015 and altering it are more likely to have occurred by then.
Casual Person
Here is what you say: "perhaps it took time for the time lines to adjust." What kind of time would timelines take? Time is time, it doesn't take time to change the timeline. That doesn't make any sense. Some people claim it was the DeLorean itself that came back to its own original timeline and only then reset itself in the new one, but then the new timelines being erased later on wouldn't have happened either. So its a genuine plot hole.
lionhead
It's established in the first film that it takes time for the changes to take effect. Marty and his siblings slowly disappear from the photo, rather than instantly. Although the scene in BTTF2 was deleted, it was filmed showing Biff dying and slowly fading away after his return to his present.
Yet they were restored instantly without any outside influence at the end of the movie. There are a lot of things wrong with this movie and the first one. Old Biff disappearing should mean that Marty and Doc should slowely disappear as well, even the DeLorean. But they didn't, that doesn't make any sense. The point is there is a plot hole, somewhere. To know where all you can do is look at it logically and then you automatically come up with Old Biff going back to the future but not the alternate future. If he did there wouldn't have been a movie, but that's the plot hole.
lionhead
The timeline didn't change until he made his first bet which was some years I think after receiving it. He immediately travelled forward after giving the act, meaning he will still jump forward to the original future.
The timelines would instantly change, and Old Biff couldn't possibly have returned to "normal" 2015. It's just a poorly-thought-out time travel plot hole (or a deliberate error to expedite the storyline).
Charles Austin Miller
Suggested correction: In context, Doc was saying that they couldn't return to 2015 to stop Biff from stealing the time machine, because Biff didn't steal the time machine in the alternate 2015, he only stole it in the original 2015. Marty and Doc didn't stay long enough in 2015 after Biff returned, and that's why they didn't see any differences. Also, though they were unaware of it, Biff was dead in the alternate 2015, so the disasters he caused might have reverted back after his death.