Up until very recently (I'm now 25) I thought the line in the song Brown Eyed Girl by Van Morrison was ' going down on the old man with a transister radio' .....the line is actually ' going down the old mine with a transister radio'......obviously it didn't make sense when I was little, but when I was a teenager I just accepted what I thought I had heard and came to the conclusion that Van Morrison was just plain dirty.
A childhood belief about misheard lyrics

others believed things like this
- I swear I heard a Disney Channel/Radio Disney song where the chorus was a repeated “Damn it”— SpengBab
- I use to believe all the people singing on the radio were IN the radio.— Yvonne
- i thought the line "saving my face" from the KT Tunstall song of the same name was "shaving my face"Anon
- I used to believe that when a song came on the car radio, the band was sitting on top of our van.Anon
- I thought the line in the song "more than a woman" was "four-legged woman".— boo
- I used to think that when a song finished on the radio it would play again on the next station— Maria