My best friend of 20 years believed when we were kids that the song by Bon Jovi "Living on a Prayer" was actually called "Living on a Prairie". My dad still thinks that is funny to this day.
A childhood belief about misheard lyrics

others believed things like this
- My mom called the dust under my bed kitties i believed there was kitties living under my bed.— Kathy
- I believed that the inside of a tomato was a small, living creature and I flatly refused to eat that bit.Anon
- My Mum told me she invented skipping and I believed her and told all my friends - still living that one downAnon
- My brothers friend still thinks he will be a kangaroo when he grows up and he's 9!!!!!— Jane Rom
- I used to believe that in the Christian Prayer of the Faithful, we were responding, "Lord, harrow prayer."— Smelleanor
- That there was a zombie living behind the bathtub in the upstairs bathroom.Anon