I thought the whole of the island of Ireland was Northern Ireland, and that therefore "Southern Ireland" was a completely different island, namely Madagascar.
A childhood belief about places

others believed things like this
- I used to believe that Ireland was called that because it really is an island!Anon
- When I was young I thought the IRA was like the IRS and that Ireland was overrun by irate tax collectors.— jhager
- I used to think that County Durham was in Ireland.Anon
- I used to believe lepers came from Ireland. Like leprechauns, only with less body parts.Anon
- I used to think that Alaska was an island!— Draqula
- i used to believe that 'island' was pronounced 'is-land' instead. I know im not alone on that one! :)
— Da KornMeal