Never have personally, but ......
One night back in high school I was hanging out over at a friends house pretty late at night. His younger brother had been in bed for hours so we were pretty surprised when he comes walking out into the living room with a very weird look on his face. We were even more surprised when he went into the kitchen, opens the fridge door, and proceeded to "relieve" himself, and then went right back to bed as if nothing happened. This kid was probably 13 at the time and he didn't remember anything the next day, but his mother sure didn't appreciate it. They took him to get help eventually because there were similar incidents with closets months later, and sometimes he would just go right out the front door and they would find him sleeping in the neighbors yard down the street.
Very strange to say the least.