The song "American Pie" by Don McLean has the lyrics:
"While Lenin read a book of Marx..."
I thought it was:
"While Lennon read a book of marks..."
Something about John Lennon and a tally sheet or something.
I also thought the next line, instead of "...dirges in the dark" was "Sturgis in the dark", because my dad was a Harley enthusiast.
It also took me awhile to realize that the song was about Buddy Holly (man, alot of people post about him on here).
A childhood belief about misheard lyrics

others believed things like this
- I used to think that Lenin and John Lennon were the same person.— Melanjolly
- I used to believe if you read a book in the dark, you would go blind.— Ellen
- I used to think that the Beatles broke up when John Lennon died.— Shirley B.
- When I was little I thought that Buddy Holly was called Bloody Holly!— Catherine
- I used to think Buddy Rich was called Buddy Rich because he was my dad's friend, same with Buddy Holly. Anon
- if you read the bible in the dark your eyes would pop out— chriistabelle