When I was younger, my parents somehow convinced me that when you felt like you had already done something before, you were having a ménage à trois, instead of experiencing déjà vu.
A childhood belief about foreign languages

others believed things like this
- When I was younger I asked my parents:
"If bees make honey, do flys make marmalade?"— Mike - a friend was convinced that his school was an asylum, and couldn't be convinced otherwiseAnon
- My 6 years younger sister used to tell me that I was younger than her. She was just growing backwards.— Taryn
- I used to think I was the prettiest girl in the world and I felt really guilty for it.— Princesa
- When listening to the radio in the mornings I felt sorry for singers they had to come and sing that early. — Tereza
- Ironically my parents were born on the same day; so growing up, I thought all parents had the same birthdays. Anon