There was a song I misheard when I was really little. I don't know the title, but I thought it went like this:
I tut (like king tut) you once, I tut you twice
A walnut cold at any advice
(That's all I remember. I wrote down my wrong lyrics somewhere, and it was at least the whole chorus.) I always assumed it would make more sense when I got older. And it did, but only when I found out it went like this:
I touch you once, I touch you twice
I won't let go at any price
(at least, I think--my hearing's better now, but I've never really looked it up.) I don't think that would have made sense to the little kid me either ;)
A childhood belief about misheard lyrics

others believed things like this
- I thought it was impossible for anyone to lift more than their own body weight. Just seemed to make sense..— Xenomorph
- I used to think that the title of Barry Manilow's song "Looks Like We Made It" was "Looks Like Tomatoes".— close2nd
- I used to think that walnut furniture was made out of the shells.— Cambria Consuelo
- I used to think that the priest at church was JESUS.
He had a beard.... it made sense— Joe B - I used to believe that broccoli grew on trees. It looks like a tree, so it made sense, right?— Catherine...
- when i was 2 or 3 believed that i had lots of animals in my tummy it made sense my mum had baby in hers.— kjc