At the risk of feeling stupid, I'm gonna admit that I wasn't all that young when I had this misconception -- after all, bag clips or chip clips haven't been around all that long. Anyhow, I used to be really puzzled about bag clips with magnets on them. The magnets are never strong enough to hold a bag on the refrigerator with any substantial amount of chips or other content in it. So I wondered why they bother to put magnets on the clips if they aren't strong enough to hold a bag on the refrigerator. Eventually I realized that the magnets are to hold empty clips on the refrogerator so they'll be convenient for when you need to put one on a bag, not for hanging actual bags on the refrigerator.
A childhood belief about around the house

others believed things like this
- I used to believe that when you put toast in the refrigerator, it turns back into bread. — sambot
- If you hold your breath and make a wish under a highway tunnel it will come true....I still hold my breath :)— aj
- I used to think that the starwars weekly comic wasn't very strong.. duh.— TAM
- when i was a little kid. i used to think that when u hold ur breath ur heart stops.. LOL :P — Annonymus
- I used to believe that it was the law to hold the railing when you're walking down/up stairs— Brit
- My dad always told me to never hold my sneeze and if I did, then my head will explode.— anon.