A few days ago I re-watched the 1993 movie Demolition Man, starring Sylvester Stallone and Wesley Snipes. I last saw the movie somewhere around 1995 or so. When I re-watched it, one particular scene left be perplexed.
The villain of the movie, Simon Phoenix, played by Wesley Snipes, is at some kind of public communication booth, when the police arrive and confront him. After he ignores their first command to lay on the ground, the police officer repeats the demand:
"Lie down on the ground... or else!"
I remember vividly Phoenix turning around and asking the police officer: "Or else what?" and the police officer becoming perplexed and asking his fellow officers in a lower tone of voice the same question. I do not remember exactly the response he then gave, but it was probably something like "or else we'll force you", and then Phoenix taunting them, with a fight ensuing.
I remember this vividly, like it was yesterday. I even remember Phoenix's facial expression and mannerisms when he asks it, as well as the police officer's. If prior to re-watching the movie I had been asked if this scene existed, as I described above, in the movie, I would have been willing to bet actual money that that's exactly what's in the movie.
To my complete puzzlement, however, that doesn't happen in the movie. After the police officer says "or else!" Phoenix just looks at him and then ignores him and doesn't say anything. That's not at all how I remember it happening!
Maybe it was an alternate scene? Doesn't seem to be so. I have searched high and low for alternate and deleted scenes, or any sort of reference to him asking that "or else what?", but nothing. I can only conclude that he never says that, and the ensuing short funny reaction from the police officers doesn't happen.
Yet, I can't help but remember that so vividly!
A somewhat memetic explanation for these is the so-called "Mandela effect", which posits that at some point in time some people have swapped places with their alternate selves in an alternate parallel universe where there have been subtle differences, and they occasionally still get flashbacks and memories of those differences.
In actuality what I believe has happened is that I imagined in my mind, perhaps during the movie or shortly after it, him asking "or else what?", and my brain concocted that little continuation there, and now, decades later, I am misremembering and thinking that it actually happened in the movie, when in fact it only happened inside my head.
I have another example, but this time it's even worse:
Something like a year ago I re-watched another movie that I hadn't seen in a long, long time: The 1957 classic film 12 Angry Men.
There were many scenes in the film that I remember vividly and clearly, such as the scene with the switchblade knife, and the scene where they recreate the limping man walking to the door of his apartment, and the argument about the woman seeing the murder through the windows of a passing train. I also remember vividly the final scene of the movie: The accused is sitting at the defense's table, completely broken with all hope lost, looking at the ground. But when the final verdict of not guilty is announced he looks up in complete surprise, with an expression that says that he cannot believe what's happening.
Except that that final scene never happens in the movie. It's not in the original script, and it's not any sort of alternate or deleted scene. To my knowledge it doesn't even happen in any later remake of the movie.
However, this time I'm so certain that I have seen that scene that I do not believe it's just my imagination and a fabricated memory. What I strongly believe has happened here is that I have seen some other movie, maybe a made-for-TV movie or similar, that has that ending scene, and I am simply confusing it with the 12 Angry Men movie. I have tried to find what other movie that scene might be from, but I have not been successful in finding it (even after asking for help in a dedicated forum). However, I'm certain that I have seen that scene. It's probably just from some really small and obscure made-for-TV movie, or perhaps some TV series, and it's really hard to find which just by googling.
Many people have similar experiences: They could swear that some movie, or TV series, had a particular scene, they are so sure of it that they could bet money on it... yet when they see the movie again years or decades later, they are left perplexed when the scene never happens (or happens very differently from what they remember). They are so convinced of it that they start suspecting it must have been cut or altered, this being some kind of alternate version or something.
What I believe is happening in the vast majority of cases is that people are either simply misremembering (eg. having imagined the scene in their heads and then decades later thinking that it actually happened), or are mixing two different movies together.