NPR did a story (maybe it was Science Friday?) about false memories. Some scientists think it could be caused by the fact that brain cells are constantly being rewritten. That is, the neurons today are not the same ones we had a year or two ago. And (ironically) like modern solid state hard drives, the memories in our brain are constantly being regenerated and stored in newly-created neurons. When that happens, it is possible for them to be incorrectly mixed with other memories.
http://www.npr.org/templates/story/story.php?storyId=4486533

My very strong, probably false, star wars memory is the 1977 presence of the deleted hangar scene (the one that was added back - slightly shortened - into the SE). I saw SW four times in 1977, one in 70mm and three in 35mm (not in that order), and I remember it so strongly I could recite the dialogue. I have come to accept that I probably saw it somewhere else, around the same time.

I think that the most compelling argument against these memories being real, is the diversity of them. There’s no way so many versions of Star Wars could have hit the theaters.

Since joining this forum and resigning myself to the fact that my memory is probably false, I have been careful to observe other instances in my life where I have provably false memories. Since then I’ve probably had at least 5 or 6 such examples - versions of my experiences that I had believed for years, and were utterly proven false. Things like, my mom did this, and it turned out my aunt did it. Or, I saw a certain thing in my backyard, and it was actually at school. The brain is a complex beast.

Heck, Trump remembers people partying in the streets of New Jersey after 911. I don’t think it’s a lie, I think it is a false memory, with his regenerating brain cells mixing in memories of Palestinian celebrations.
http://www.politifact.com/truth-o-meter/statements/2015/nov/22/donald-trump/fact-checking-trumps-claim-thousands-new-jersey-ch/