Whenever I the movie Titanic first came out, I pretty much fell in love with the song "My Heart Will Go On"...but instead of "Far across the distance, and spaces between us" I thought it said "Far across the distance and spaceships between us." It for some reason made sense at the time.
A childhood belief about misheard lyrics

others believed things like this
- I used to think you could have a heart attack if you fell in love too deeply!Anon
- I used to believe a mile was the distance between telephone poles.— Allegra
- Airplanes got places faster because it was actually a shorter distance up there.Anon
- I used to believe that the heart at the beginning of the I Love Lucy Show was made of real chocolate.— Krissa
- I thought the song "Party Time" by Moby was actually saying "heart attack" (this was before I knew the title)— Elviessa
- The song called heart of glass mixed me up as a kid. I heard "Heart and ass". — oops