I think they're should be a section called "Cows and bulls are 2 different species" because I used to believe cows are often male, and that bulls are a different animal.
A childhood belief about general

others believed things like this
- I always believed there were boy cows and girl cows and boy bulls and girl bulls— karen
- When I was little I thought cows married horses, cows were all female and horses were all male. — Sheila
- sterilised milk came from bulls— kate mullins
- I used to believe, as a child, that horses were male cows.— Martin Taylor
- I used to believe chocolate milk came from brown cows and regular milk came from black and white cowsAnon
- i used to think chocolate milk came from brown cows and normal milk came from white cows Anon