I used to believe that certain babies were born with extremely huge shoulders.
These babies were sent to "training camp" (which is why you never saw them on the street as children and when they grew up the became professional football players.
A childhood belief about sport

others believed things like this
- When I was little, I used to believe that football players really had shoulders that big.— Angie
- When I was a kid, I used to think that the only way you could play football was if you had giant shoulders.— Sam
- I used to believe that babies were born out our bellybuttons.Anon
- When I was a child I used to believe that the the babies were born from the seeds. — Rosimeire
- That the belly button was the place where babies where born from.Anon
- In the mid 90's, I used to believe that babies who were born in the year 2000 would live forever.Anon