The Berenstain Bears were actually the Berenstein Bears and nobody can convince half the internet otherwise.
Nelson Mandela apparently died twice. Darth Vader never said "Luke I am your father." And don't even get people started on whether Curious George had a tail or not because friendships have ended over less.
The Mandela Effect has turned everyone into part-time detectives arguing about fictional details with the intensity of a courtroom drama. People will fight to the death over whether Monopoly Man had a monocle. They'll swear up and down that Shazaam was a real movie starring Sinbad as a genie even though it absolutely was not.