I haven't had this happen to me, but I want to experiment with it. I took a few Mandarin classes, and I'd really like to have a fluent DC I could practice with.

An acquaintance of mine claimed that while sleep walking/talking, she had a conversation in Italian with her father. The girl didn't know any Italian, but her father was proficient. However, she was not LDing, and she had been to Italy in the prior year. Naturally she heard Italian pretty regularly when she was there. It makes you wonder if she knew what she was saying, or if she just was lucky enough to pick a few phrases that made sense.