From the time I was a child, I believed penguins were man-sized. All the pictures I ever saw of them they were standing on ice, with nothing to reference their size. I am 57 and it wasn't until a few years ago that I learned differently.
A childhood belief about birds

others believed things like this
- I used to believe that penguins could fly, they just didn't want to.— Mariah\
- When I was little I thought that pancakes were made out of penguins. — Monty
- I used to believe that penguins lived in the back of my freezzer— JOE JOE
- I use to believe that people who wore tuxedos were actually wearing the skins of Penguins. — Keith
- I used to believe that everyone in pictures could see me so i turned all of the pictures in my house backwardsAnon
- I used to believe that since guys peed while standing up, then they must poo while standing up too.— Stupid girl