I thought that the song "Lyin Eyes" by The Eagles was really "lion eyes", and that it was about a person who was secretly a lion.
A childhood belief about misheard lyrics

others believed things like this
- I used to think that a sea lion was a hybrid of a seal and a lion.Anon
- when i was little i thought my cat would turn into a lion when he got older.Anon
- The Kim Carnes song called 'Bette Davis Eyes' well my dad used to sing "She's got Dickie Davis Eyes" Anon
- I used to believe that the meat dish 'tripe' was lion.— Kent
- when ever i ate broccoli i thaught the monkey from Lion King was in there— Simon
- I was born brunette with brown eyes and dark hair, i thought people with blue eyes, had water in them.Anon