It wasn't me but my grandmother used to believe that everybody spoke Catalan and Sapnish. And thus she would say things like: How intelligent the Brittish children are, they are so little and they already speak English!
A childhood belief about foreign languages

others believed things like this
- I used to think that even people who spoke something other than English, thought in English— Peaches
- I used to believe that everybody spoke English in the worldAnon
- I know my dog, Palmer, spoke English, he was just really quiet.
— Klayne P. - I used to believe that the whole world spoke the same language- English.Anon
- I used to believe that my dog could speak English, but he just didn't feel like it.— Mariah
- I used to think that adults spoke an entirely different language (not English) when kids weren't around. — Swordfish