Okay. An odd one here (or perhaps not... we'll soon see based on responses
)...
DS2 has a 3DS game. He loves to play it. That's fine. We try to limit the time he spends on it. But...
he spends ages digging through the activity log, trying to change settings on it, looking through the manual, and CHANGING THE LANGUAGE on it !!! 
He knows exactly how to change everything back - but honestly, sometimes I'll look over and he's playing his game and all the words are in German or French or Italian. And he's still happily playing away.... 
I don't for one instant think he has mastered or even learned these languages, by the way. I suspect he has memorised where all the specific buttons/controls are on the screen for each game, so doesn't NEED to know what the word say IYSWIM.
Anyone else dealing with this?
DS2 is also obsessed with the idea of learning another language. When he is rattling off speaking so quickly I can barely figure out what he is saying in ENGLISH.. god help me if he learns another language!! I'd have to learn it as well just to keep up! 