The chorus to the song "Freshmen" by The Verve Pipe says
"We were only freshmen" ... I had a friend who would sing "We were only FLESHmen"
In the song "Busy Child" by The Crystal Method, there is a line that repeats a lot that says
"I guess I didn't know" ... the same friend misinterperated this as "I guess I didn't notice"
Not that I haven't had my share of misunderstandings of a lyrical nature... a few classics are:
White Zombie's "More Human than Human" -- "More human than you, man"
Gin Blossoms "Hey, Jealousy" -- "Hey, Chelsea!"
and in "Daria" by Cake, John McCrea sings the words "icing on a cake" at one point... for years I thought he was saying "I sing on a cake" ... what a revelation that was, when the truth dawned on me!
A childhood belief about misheard lyrics

others believed things like this
- I used to believe making a cake from scratch meant using a box mix rather than buying a cake from the store.— EZ
- I used to believe that a fish cake was a fish in sponge and coated in icing. I believed this until I was 9.Anon
- I used to believe that on your birthday, you didn't advance to your next age until you ate your birthday cake.— Casi
- when i was 4 i thought an earthquake was an earth cake!— chardog
- I thought that Devil's food cake was invented by Satanists!— Dietrich Corby
- when i was little i used to think i was the only human and everyone else were robots trying to act human.— Spikey