When I was little I used to think that the "use by"/"best before" dates on food products were actually the date when the food was made! I thought that a lot of the food had been made in the future somehow...
A childhood belief about general

others believed things like this
- i thought salt made food cold, since pepper made it *hot* — cattiva
- I thought when you got food poisoning it might someone had put poison in your food— Bootlebat
- I use to believe that salt would cool food down while pepper would heat your foodAnon
- I used to believe when ordering Chinese food the food and delivery man came from China— Dave
- I used to believe that tofu was actually called "toe food" and that it was made out of toe-jam.Anon
- I used to believe Mexican food was made from real Mexicans!— Holly W.