I used to think that all people who were called "John" were actually named "Jonathan" and "John" was just the shortened form of the name. Same thing with "Chris" and "Christopher", as well as "Alex" and "Alexander".
A childhood belief about names

others believed things like this
- I used to think that Olivia-Newton John was three people like Sharon, Lois and Bram....Olivia, Newt and John— J
- As a child I used to think that Olivia Newton-John and Elton John were married.
Boy, I was way off.— Lisa - I used to think that Olivia Newton-John was 3 people: Olivia, Newt, and John— Sally
- As a child, I thought that Olivia Newton-John was Elton John's wife and Juice Newton's sister.— Connie
- I thought that Olivia Newton John was a group, Olivia Newt and John. — Sam O.
- I used to believe the the Elton John song, "Crocodile Rock" was about a Crocodile, named Rock.Anon