When walking along or unconsciously stimming by running about the room, I often get so lost in fantasy conversations between the person who's my special interest at the time and another person, or between any two people about an abstract subject I'm analysing, that my face and mouth act out the conversation. The words don't come out loudly, clearly or completely, so no one can hear specific words, but I'm told it's very bizarre. I'm usually only lost in my fantasies enough to do this when completely alone or with only family around, so my family see it sometimes. My sister gets irritated by it and says "you're going nutty again, stop going nutty".