When I was 9 or so I knew that the people kissing in movies weren't really married. So when I saw my first movie with a sex scene, I was scandalized that these unmarried people were having sex!
Fortunately my friend's older sister was there to explain that there were things called "rubbers" that the actors used, so nothing really touched and it wasn't really sex. What a relief.
A childhood belief about films

others believed things like this
- I used to think actors in movies sometimes had to actually die to make the movies look real.— Dero
- That people older than me knew what they were talking about.— Mark
- i used to think that every family had a brother and sister and they married eachother when they got olderAnon
- I used to believe that people from Holland were called "Hollish", like people from Poland are called "Polish"— Sally
- Based on that memorable scene from the "Wizard of Oz," I used to believe that people died from shrinking!— Julie
- a friend of my little sister's had 4 older brothers, so she thought that when you got older you grew a penis!Anon