I believed until I was 17 that blankets were inherently warm. They seriously aren't. They don't generate heat at all.
A childhood belief about around the house

others believed things like this
- That blankets had some magic quality that made it so you could become warm and stay that way— Michael
- I used to believe that the heat from the furnace came from hell, and that it was a straight drop there.Anon
- I used to think what heated the food in the pan was the boiling water, not the heat under it.— Mario
- 'I've got candy in my ears tonight, baby'.
~Canned Heat, Jimiroquai.— Nin - I thought that cold was an actual, positive force and not just the absence of heat— terberous
- I never did understand why it was "Our Father, who aren't in heaven".— Edith