They call it the Mandela Effect. That's when you have a false memory. You probably don't even know that your memories aren't real. Still, according to a study from the University of London, about 40% of your memories are fake. That time you went on a date to see Titanic, the weekend of your graduation in '95, didn't really happen. That movie didn't come out until 1997.
We all remember the famous line, "Luke, I am your father," even though he actually said, "No, I am your father." That is a perfect example of the Mandela Effect. It's a large group of people remembering something one way when it was actually another. It's named after Nelson Mandela, who many people thought died in the 80s.
A strong false memory I have is the local Albertson's grocery store commercial. The one where they sang, "It's Joe Albertson's Supermarket..." I vividly remember an older bald man sing, "I'm Joe Albertson, and it's my supermarket..." There is no record of this—plenty of videos of other people singing, but not Joe.
The Mandela Effect has its own convention. This year's event was canceled due to COVID, but last year's event was documented recently on HBO's How To with John Wilson. It was an episode titled, "How To Improve Your Memory." They could have chosen anywhere in the world to hold the convention, but they chose Ketchum, Idaho!
The show has bizarre pacing, but I love awkward and have a dry sense of humor, so I love it! If you have HBO Max, you can watch it on demand.