I used to think that in a sentence in French, no word or beginning of a word can be capitalized. So if i would say, I like Bob. in french, i thought it would be j'aime bob. instead of J'aime Bob. Turns out it was only for dates that capitalising months and days was not allowed.
A childhood belief about foreign languages

others believed things like this
- I used to believe that french kiss was something coming from France, and that only the French did it— Sasha
- I used to think that you had to be french to really taste french fries.— Not French;)
- In first grade, I thought that if I've never heard of a word before, then it wasn't a word.— Destiny
- I thought french fries were really invented in France (they are Belgian for those who don't know)— Quarm
- When I was young I thought that police had soft skin, because this is how it sounds in French " Peau lisse "
— amine - i used to think that french was english backwards!— ---pepsi---