Not from my childhood, but worht a mention. Last year when I had heard Nightwish' song "Wish I had an angel", I remember I misunderstood the line "Beauty always comes with bad thoughts" and thought it was "beauty always comes with buttocks" =) Really!
A childhood belief about misheard lyrics

others believed things like this
- When I was about 5 or 6, I used to think the song 'Beauty and the Beast' was really 'Beauty and the Beef'.— Natski
- when I saw those prepare to meet thy god signs I thought they were beauty parlours for religous ladies only!— knuckles
- I used to believe that beauty marks (freckels) were Butterfly bites!— Jolene
- When I was a kid, I believed that bible school was "beauty school", and called it that all the time.— Dana
- Since my father had a deep cleft in his chin, I thought he was growing a tiny buttocks out of his face.— Rick
- When I first heard Bruce Springsteen's song, "Born in the USA," I thought that the song was "Porn in the USA"Anon