Up until I was over 30 years old, I believed that in the Eddie Cochrane song 'Drive In Show', he was singing 'Bet my penis to a candy bar, you'll be cuter than a movie star'. It seemed a bit overly racey for the 1950s to me, and I wasn't 100% sure that I was hearing it right. But I couldn't think what else it could be, so assumed I must be right. Until my wife pointed out that if you substitue the word 'peanuts', then it makes a whole lot more sense! ok, I suppose so...
A childhood belief about misheard lyrics

others believed things like this
- I thought the lines in the sky left behind by airplanes were "sky scrapers". Makes sense.Anon
- I thought a major general is more powerful than just a general (which still kind of makes sense to me)— Demond
- In first grade, I thought that if I've never heard of a word before, then it wasn't a word.— Destiny
- In the song "Let's get it on", I seriously thought they were saying "candy on Crome". — Kate P
- I couldn't understand why my grandmother wore an ear-grenade (hearing aid). It sounded very dangerous to meAnon
- I thought if you took some candy and buried in the yard, you would grow a candy tree.Anon