The Mandela Effect
It's a phenomenon whereby many people recall the same memory that never actually happened. It is so named because a lot of people seem to remember Nelson Mandela dying in prison in the 1980s.
The most common examples of this are:
"Hello Clarice" from Silence of the Lambs - Hannibal Lector never actually says this
"Mirror! Mirror! On the wall!" from Snow White - she actually said "Magic mirror on the wall"
Berenstain Bears - many people remember them as the Berenstein Bears
And there are some people who theorize that the reason for this is that the Cern Large Hadron Collider has altered our universe in some way, or shifted us to an alternate universe.