Yep, same scenario here. he'll repeat the same word or sentence in French for me, or in English for his father. He gets upset with me if I tell him, while reading a book in German, that the butterfly is a "Schmetterling". He'll look at me, frown, and say, "Non, c'est un papillon." He used to do that between English and French, but he has accepted the duality at this point. The other funny thing is when he says something pretty much unintelligible and you try to figure out which language it might be in. For a while, some time ago, he had me stomped with "Blanquette". He kept saying the word, perfect French accent, and I thought: How could he possibly know this dish (it's a veal dish with a lemony cream sauce). I wouldn't put it past his father to start reading cookbooks to him at night. Only to figure out, silly me, that he meant "Blanket". Our current riddle is the word "Bouge", which he says when he sees snow or mountains.