My dad, who has since passed away, believed up until his 30s that a donkey was just a horse with long ears.
He also believed (because my uncle told him this) that there was a special breed of "hillside cows" with one set of legs (on either the left or right side) shorter than the other, so that they could stand straight on hills.
But if you put them on level ground, they could only go around at a tilt, and in circles.
A childhood belief about general

others believed things like this
- I believed that the breed of dog called Boxer was called that because they could stand up and box.Anon
- a donkey is just a small horse.Anon
- I used to belive that Donkey's were a type of horse. How stupid of me lololAnon
- I believed for a long time that brown cows gave chocolate milk!— Evil Mom
- I used to believe that cows mooed out of their ears-because my older sister told me they did.— ella
- i used to believe that if i didn't work at school, i would have donkey ears, so now i work hard !!!— denis