I was once convinced that if you were to trap a bird in an open plastic bag, its attempts to fly upward would lift you off the ground.
A childhood belief about birds

others believed things like this
- Street signs with the upward pointing arrow was for airplanes. — Tammy
- I used to think that doctors added plastic to your face in plastic surgery.— caro
- I used to think that plastic surgery actually involved using plastic.
— JohnJ - I used to believe that plastic surgery was done with plastic knives.— Vicki J.
- I used to believe that if you put your hand in a venus fly trap it would eat it.Anon
- I thought ground beef was the meat they scraped off the ground at the slaughterhouse. Yuck.Anon