I used to believe that people with certain combinations of names, like "Carla" and "Melissa", for example, or like "Tammy" and "Lucy" were mutually invisible to each other, couldn't interact with each other in any way, and would be totally unaware of each other's existence. But then later I knew of a Carla and a Melissa who were each other's best friends. So they clearly knew about each other and interacted with each other. So after that I gradually got over that belief.
A childhood belief about names

others believed things like this
- I thought that the line was "Lucy in the Sky with Linus" (not lucy in the sky with diamonds)— Forrest
- I used to believe that all famous people knew each other.— Liz
- That people older than me knew what they were talking about.— Mark
- I used to believe that the way you knew when people were dead was when their toungue was sticking out. — Geneva
- when i was a lil kid i used to think salt was dead lice that people but on there food and i never knew why
— jessica diamond - Before I knew about death, I used to think people turned back into babies again after they got old. Anon