I've had a few dreams in which japanese was included. I've been trying to learn japanese for quite a while, with little success thanks to college, homework and such. I'm not fluent by any means but i know enough that i may use a little japanese in a dream or a dc uses it. It is usually very brief because my knowledge of japanese is fairly limited. I've never had an entire dream in japanese before, but i definitely would like to. The interesting thing is that i know more japanese subconsciously than i realize. I may use a word or phrase that i didn't "know", then when i wake up and recall the dream i'll think, "Oh, that's what that word meant" or "That's what that word was." It's almost like my subconscious is teaching or helping my conscious review parts of the language.