This isn't mine, but my friends instead. When she was little and travelling in the car with her parents in the country she spotted some cows. She got excited and pointed and said "Daddy! Lookie, cows!" and her dad replied, "No sweetie, those are chickens." And for a while she thought that cows were chicken and always called them that. XD
A childhood belief about general

others believed things like this
- When I was little I thought cows married horses, cows were all female and horses were all male. — Sheila
- 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
- I used to believe that brown cows made chocolate milk and white cows made regular milk.— andrew mient
- One of my friends told me that when he was a kid he thought windmills were used to keep cows cool!— Julie
- I used to believe that cows laid beef, like the way chickens laid eggsAnon