The misinformation effect is when a memory becomes skewed after hearing false information about the event.
An example of this when my high school cooking teacher told the class that she watched a history channel show on Italy and how they said that Italy’s circumference was only 30 miles. She exclaimed “That’s how small Italy is! That’s from here (Carson City) to Reno! That’s the whole circumference!!”
Apart from purely being an idiot, I believe my teacher was a victim of the misinformation effect. I believe that someone, probably her husband, told her that Italy had a circumference. He then told her that the circumference was only 30 miles. Later, when Italy came up, she remembered that the man on the show told her this false information. Poor lady.