Visiting some friends of my parents at their lake cabin, I went for a walk in the woods with their daughter (a couple years older than I). We found this little reddish object in the road, and she told me it was the heart of a dead animal. She pointed to the holes in it where the "veins" entered, sounding very authoritative, as if she'd seen plenty of animal hearts lying in the road.
She had me grossed out for a few minutes until she finally laughed and admitted, "It's a <i>peach pit</i>, dummy!"
A childhood belief about general

others believed things like this
- I used to believe an artichoke was an animal and we only ate its heart. — Laura
- I used to believe that if you swallowed your gum that you would crumble up and smell like a dead animal !!!!— jordan
- I used to think that if you went to the end of a road marked "Dead End", somebody would try to kill you.— Spooky
- I used to believe that a vitamin was a small animal
only recently I have found out that it is not true... :)— Sylwia - When I was a child, I used to think that if you eat an animal, you become that animal
— Hmza - i always thought that a DEAD END sign
as where they put all the road kill.
— pav