Well I believed that the song 'Constant Craving' (by KD Lang, I think) was actually can't stand gravy!! And sang these words right up until my husband pointed the correct words out to me about 3 years ago!!
A childhood belief about misheard lyrics

others believed things like this
- When I first heard the song "Constant Craving" by KD Lang, I thought she was singing "God save gravy."Anon
- I used to believe that all four-letter words are bad words.Anon
- My mom used to say that if I said bad words, poop would appear in my mouth— Nina
- I thought "prison" and "prism" are the same words as each other.Anon
- I thought the word economical was actually two words: eek and omical.
— Nancy M. - When i was in kindergarten, i used to think that i invented the words million and billion— Comonsnadama