I used to think that when a film was being made, the actors had to act out the whole thing in one take. If someone said their lines wrong, the whole film would have to be redone.
A childhood belief about films

others believed things like this
- I used to believe that an animated film meant that the film had live animals in it.— reverb
- I used to beleive that in order to rewind a film the actors would have to re-act the whole movie backwards. — movies backward
- I thought cartoons were real, I remember asking my mom why there were lines around the "actors" in a cartoon.— Steven Graziano
- 'To Be Announced' in the TV guide was a film that was on all the time!— Clare
- I used to think that a Mormons were an alien race from a fifties sci-fi film.— Katherine
- When a grown-up is shown as a child, it was actually them, and the film took 20+ years to produceAnon