In the US, pillows and mattresses have a tag on them that says :
UNDER PENALTY OF LAW THIS TAG IS NOT TO BE REMOVED EXCEPT BY THE CONSUMER.
I used to belive that it was illegal to ever remove the tag from mattresses and pillows. I thought that even if you bought it you still couldn't remove the tag or you would go to jail. ( I didn't now what a consumer was then)
Once the tag came off my pillow. I ran crying to my mom, terrified that I was going to be arrested. She calmed me down and explained that the tag only had to be left on when the pillow/mattress was being sold at the store.
A childhood belief about criminals

others believed things like this
- I used to believe that drug stores sold illegal drugs and I couldn't work out how they got away with it.— Bigg Jase
- I thought drug stores sold drugs. I never understood how they could sell illegal drugs.— Diana Rios
- I used to believe in Perez mause when my teeth fall, I put them under the pillow to see what happened— AyrtonZ01
- My sister used to sing Kylie's "cheese on my pillow", somehow tears works better.— Tom
- when I was little I believed that if I put a white stone under the pillow with my tooth I make more moneyAnon
- My nephew refuses to put his tooth under his pillow in case the fairy burns him with her wand.— Nina