When I was a kid, I used to believe that it was possible for people to clean their eyeball the same way cartoons do, to make them brighter. Well I've never tried it, but I was still keeping this idea until a certain age though!
A childhood belief about eyes

others believed things like this
- I used to think that when people were taking their contacts out that they were taking their eyeball out :) — Jen
- I used to think that "cross-eyed" meant that people had X's for eyes, like dead people in cartoons.— Tim
- I used to wonder why people didn't have outlines like they did in cartoons.— Anna
- I used to believe cartoons were real people and animals. They were just wet.— Wendy
- I used to believe cartoons where real people. You can imagine how that went... — Emma
- I used to believe that the sun shone brighter on a Sunday! Sunday in all languages is named after the Sun!!!— Vasu Moses