I used to think the song that goes "Call me Mr Vain" was "Call me Mr Vein", when I was very young.
I thought it was some stupid medical song designed for kids until I heard the rest of the song many years later.
A childhood belief about misheard lyrics

others believed things like this
- When I first heard Bruce Springsteen's song, "Born in the USA," I thought that the song was "Porn in the USA"Anon
- I thought the song "Karma Police" was actually saying "call the police" before I learned the title— Alberto Richardson
- i thaught the michael jackson song billy jean song said Janet's not my son Anon
- When I first heard the song "Constant Craving" by KD Lang, I thought she was singing "God save gravy."Anon
- "Yooce cream, ice bean, we all scream for ice cream!"
This song was always stupid to me.— Shirley B. - In a religious song, instead of “Jesus Christ” I heard “Cheese is Prize”— EJ