My friend Helz has a lot of these, but my favourite was when she thought the line from Summer Nights from grease "he just turned 18" was " and he has white teeth"
It really tickled me
A childhood belief about misheard lyrics

others believed things like this
- the summer that I turned 11 I waited out side on the step all summer for my hogwarts letter... ;D — Ginny weasley... not really
- Until I was around 8 or 9 years old, I thought dentists took your teeth out and replaced them with new teeth.— Verapamilo
- I always thought that "elbow grease" was a type of lubricant until about 2 years ago. I'm 19.— Erika
- I used to think the lyrics of "Boys of Summer" said "poison summer"— Lindsay
- I used to believe that eating burnt toast would make your teeth whiter and would brush your teeth for you.— Natasha
- I used to believe that if I didn't brush my teeth at night, ants would crawl into my mouth and eat my teeth.Anon