A pack of playing cards I had as a kid came with instructions for various card games. These instructions often mentioned to "discard" certain cards, and I thought they meant to literally throw those cards away in the trash. I figured it was a trick to get us to buy a new pack of cards for every game and that I was outsmarting them by keeping the cards they told me to "discard".
A childhood belief about toys

others believed things like this
- When i was little, I used to send Jesus birthday cards on christmas and thought he would read them in heaven.Anon
- I used to believe that checks and credit cards allowed you to get anything you wanted with out paying for it. — Diamond
- I thought if 3 cards stopped at a 3-way stop sign then they had to stop forever until Christmas.Anon
- I used to believe, driving in front of all the other cars on the highway, Knight Rider was leading the pack.— Michael Kolassa
- When I was a child I used to believe that when I played video games my real world changed like the game. — J
- I thought a Debit card was actually called a Debt card.— Kilgore