I used to believe that the Beatles "Let it Be" were singing "letter B" because I had heard that latter version on Sesame Street. I remember that I got into an argument with my mother over it.
A childhood belief about misheard lyrics

others believed things like this
- I used to believe that “Emo” was related to Elmo from Sesame Street.Anon
- I seriously used to believe that Bert from Sesame Street lived in my closet and that he was going to kill me.— Liz
- I heard a mother in the street tell her young son not to pick his nose...because his head would cave in. — Ruby
- When I was a kid I heard that the Beatles did acid and I wondered if they melted from it.Anon
- I thought that Count Dracula was the count from Sesame StreetAnon
- When I first heard the song "Constant Craving" by KD Lang, I thought she was singing "God save gravy."Anon