Until I was 12 I used to think the Australian national anthem ("Advance Australia Fair") was about Australia putting up the price of Australian airline tickets so New Zealanders couldn't afford them - "Advance Australia Fares".
A childhood belief about misheard lyrics

others believed things like this
- WHen I was a kid i used to believe you could dig to Australia— Chie
- i used to think that Australia was the whole world.— Trish
- i used to think that bethleham was in australia, like just out in the desert somewhere— joanna
- I was sure that Adelaide (where I lived) was the capital of Australia because they both started with
"A"— fiona - I used to believe New Zealand and Australia were part of the UK because they have a UK flag on their flags — H
- I used to believe that on your birthday, you didn't advance to your next age until you ate your birthday cake.— Casi