Sliced bread. I used to think that the when sliced horizontally (for sandwiches etc) the top half with the curved 'shoulders' was female and the square bottom half was male.
A childhood belief about general

others believed things like this
- "Better than sliced bread"
I used to believe 'Sliced Bread' was a musical band.— Madeline - I used to believe that your belly button was what held your top half to your bottom half...— Debelouwho
- I used to think that to desex an animal meant to turn it from a male to a female or female to male.— Phil
- I used to believe all cats were female and all dogs were male.— Sabby
- I used to think that all cats were female and all dogs were male. — Annalisa
- i used to believe that all cats were female and dogs were male!Anon