I am from the Washington D.C. area and when I was younger, the former Mayor, Marion Barry, was in the news quite a bit. For some reason, I didn't understand that he was just one person -- I thought it was really nice that they let a husband and wife team run the city - Mayors Mary and Barry! What is even more amusing is that my twin sister thought the exact same thing even though we never discussed it!
A childhood belief about names

others believed things like this
- I used to think that the title of Barry Manilow's song "Looks Like We Made It" was "Looks Like Tomatoes".— close2nd
- When I was little I thought that a honeymoon was when the Husband and wife went to the moon and eat honey.— AmAnDa
- When my sister's father went to Seattle, my sister said "Is Attle nice?" She thought Attle was a person's name— zzo38
- I used to believe that every person in the world had a twin, and that I had a long-lost twin in France.— Ashley
- When I was three I used to believe that cow and horse are wife and husband.— xenia
- When I was little I thought that Washington( D.C. )was in Washington state. Anon