When walking to work one morning I was waylaid by a smallish Asian woman. Saw her coming a way off. Looked fairly normal, nice bag, nice shoes, clean hair. Kind of unnotably attractive. Nothing that would outwardly proclaim "I'm a crazy person." She deviated her course a few times to end up in front of me, kind of like that awkward thing that happens when you try to walk around someone at the same time, except deliberate. She stopped uncomfortably close to me, looked up, and began babeling. Now, this wasn't just some language I'm unfamiliar with. It was a full-on speaking-in-tongues stream of nonsense. Short, one syllable repetitive "PaPaLaLaMaMaSaSaKaFaFaDaRaMaBaBaRaRaTa..." just going on like that. Her expression was pretty much blank. Not distressed, amused, or even concussed. Just calm and a bit detached. This went on for about a full minute before I finally said "I'm sorry, I don't understand you." She cocked her head slightly, and without another "word" just walked on past. If it was a lame prank she had the world's best poker face.
I still half suspect that if I listened too long I would have ended up infected with Snow Crash or something.