I used to think the lyrics to 'About a Girl' by Nirvana were 'I need a lizard friend' instead of 'I need an easy friend'. I know I'm not the only one because someone else said something to the same effect.
I used to sort of think that the words in this line of 'Sir Psycho Sexy' by the Red Hot Chili Peppers was 'I got stopped by a lady cop in my lunchable-b'. I was like, 'Why the hell is Anthony Kiedis driving bolonga?'
A childhood belief about misheard lyrics

others believed things like this
- I always thought Hot Chocolate were singing 'You Sexy PIG' instead of 'You sexy Thing.— Bilz
- I used to think Right Said Fred sung 'I'm too sexy for my lamb' instead of 'I'm too sexy for Milan'.— Nineties music was great
- My friend used to believe that the lyrics to Elton John's "Tiny Dancer" were:
"Hold me closer Tony Danza"— I'm with stupid - My friend's sister believed the lyrics to Gazza's "Fog on the Tyne" were "Fog on the dinasaurs mine all mine"— Suzanne
- My friend's mom told my friend's little sister thatI when a dog died, it went to a retirement home.— ellen
- When I was little, my dad had a friend named Scott. I thought my dad's friend was the king of Scotland— Uhhh....