On of my friends is a very heavy sleeper. One day, when he was sleeping, one of my friends asked him a question, and to our surprise he answered it. So then we kept asking him questions, mostly yes or no questions, because he didn't really speak through the whole thing, mostly just grunts, and nods. Then after a while, we tried to get him to do things. We told him that people were around and put him in different scenarios, such as he was being chased, and we told him to run, then he would begin kicking while lying on the ground (that's where he was sleeping), as if he were really running. We gave him a toy gun, and we told him that people were after him, and to shoot them, and he started "shooting" with the gun. So I'm just kind of curious as to what this is and why and how it happens.