Firstly one of my own. I used to think (up until not long ago) that the line in the Bee Gees 'How deep is you love' - 'and you come to me on a summer breeze' was 'and you come to me on a submarine'
Now my wifes and I've heard her singing these.
J. Geils band - centrefold - 'My angel on the cellaphone'
Clash. I fought the law - 'I fought the Lord'
The cure - Love cats - The line 'We're so wonderfully wonderfully wonderfully
Wonderfully pretty' translates in her mind as ' one free one free one free one free city'
Hmmm...
A childhood belief about misheard lyrics

others believed things like this
- When I first heard Matt Monro's song "Born Free," I thought he was singing "Porn Free."Anon
- When i was a tiny lad, I used to think drug free zones were places where you can get drugs for free— Spencer
- I used to think that money from ATM machines were free :p— qwerty
- I used to believe that priceless meant free.— Neo
- I used to think that "priceless" meant free.— DAAA
- That everything was free. You paid for nothing, money was just to look nice.— Blasia M