This thread's come up before, and I remember that last time around, a few people mentioned that they had been interviewed in Spanish. I would think that is one of the few languages where that might be a possibility. I'm fluent in Lithuanian, a language so obscure that no one even addressed it too much in my interview, much less asked me to speak it (12 interviews). So there's the key, claim some esoteric, obscure language that you're certain no one will call you on.