I mishear more and more with the passing years... but my two best date from a while ago:
Bohemian Rhapsody -"Spare him his life from these pork sausages!" (=Monstrosities - still can't hear it any other way though!)
and Tom Jones' 'Sex Bomb' -
"Infra-red semen shoots through the night..." (well it IS Tom Jones!!) I believe it's Infra-red, see me speed through the night...
ah well... ;¬)
A childhood belief about misheard lyrics

others believed things like this
- When I was younger, my brother told me the police had an infra-red system and could see into everyones house.— Clare, Ireland
- In Queen's Bohemian Rhapsody, I used to think they were singing "Beelzebub has a devil for a sideboard!"Anon
- I thought that Tommy Lee (the singer) and Tommy Lee Jones(the actor) were the same exact person.— Glowworm
- My sister believed the pork in pork and beans was marshmallow...and would always "fight" us for it.Anon
- At night I would hear the chirping crickets and thinking it was comeing from the stars in the sky!— delana
- I used to believe that all my stuffed animals would come to life at night.— Carrie