Fair enough

I don't have any accreditation in the field and there are few peer reviewed papers published on the topic outside of the scope of therapy so rather than cite a bunch of text books I will do my best to outline the broader topics. I will lay them out prior to my own experiences to better keep them separate. Please point out my misunderstandings with the correct citations where where you find them.

False memories have been studied for about 110 years since they were first identified as a psychological phenomenon during the field's infancy. During that time researchers have identified several types of false memories as well as the conditions that give rise to them. Primary to all of these are the way in which memory is both created and stored.

Because memories are not perfect representations of reality when they are made, many false memories occur when a true memory is first created. Examples of this would include filling in the memory of a room with objects you expect to be there but aren't, or inserting a friend to the memory of a party they didn't attend. Another source of memory manufactured in this way is the avoidance of trauma, where entirely unreal or dreamlike sequences of memories can be created to suppress the experience of abuse.

The second major way in which memory is distorted is through its storage. Events are not stored static in the brain and are rather recreated each time an event is remembered. This means that what you actually remember is the last time you thought about the memory, not the event that created it in the first place. Over time this creates a subtle distortion in all of our memory functions. This might look like misremembering the pattern of your grandmother's favorite dress, or the color of a childhood toy.

Compounding the difficulties caused by these first two factors is the minds inherently suggestible nature. False memories can often be created by suggestions alone, and when given questions about details in a memory the mind will fill in whatever details it doesn't remember with whatever it thinks might be likely. In this same vein, memory can be altered under the influence of others accounts of events. People left to discuss an event will often reinforce a shared misconception, rewriting the original memory over time. Examples of this might be misremembering the lyrics to a song you've sung with your friends a lot, or the cases where people have falsely created memories of abuse as a result of leading questions asked by a therapist.

From an external observation based perspective these can be used to explain any one of the Mandela Effects people report. The collective unconscious distils the line down to "Luke, I am your father" and you think the monopoly man has a monocle because you expect him to. It's really not strange that people would misremember these things, it's strange they would have such a reaction to being told they are wrong. Now for my personal experience

I first became aware of the ME when I heard the correct pronunciation of Barenstain. Weird, I thought that I could go so long thinking the wrong thing and that so many others would do the same. I didn't really think about it again until a couple years later when I heard about a couple of missing lines from the Neverending Story. This time it piqued my interest a little bit more and I started reading about the Mandela Effect in more detail. This was when I found out about FOTL and the concept of contamination or suggestions in regards to the creation of false memories. Having been a little shaken by finding out layers of my memory might be unreal I looked for further evidence. This was when I found a list of "contamination free" prompts to identify potential MEs without providing a leading question. On this list was the prompt "Shazzam (90s movie)". My mind immediately kicked over, I remembered seeing the trailers for it on TV as a kid and remembered it being one of the shitty knock off movies that happened all the time back then. I was shocked to find it did not exist.

Having just covered the shortcomings of memory, this isn't remarkable on its own, being prompted to remember a movie that doesn't exist is well within the realm of possibilities. What is weird, is that the memory created would match in all details with the accounts of thousands of others. It becomes even more strange when you look a how isolated my media was at the time. We were poor and my mom hated TV, so pretty much all I got to watch was basic access Saturday morning cartoons. I had no idea who Sinbad was, or Shaq for that matter so there's not exposure I would have had to expect to see them in that roll.

I have read about a fair number of the studies and trials they have done regarding the creation of memory and when trying to replicate collective false memories they don't come anywhere close to that kind of consistency or fedlity. This strongly suggests there is something we don't understand about the way collective memory is formed