I call them just "heads". The "little head", the "zombie head" and so on. I'm not sure it's the same thing you're talking about, but seems pretty close. Kind of in-between of internal and external. I told my T about it and she didn't really see a big problem with that (read: she didn't freak out or I couldn't see it). I like that I told her early about it, so I can say stuff like: that head thinks this and that head wants to do that. It's easier to work with T this way. I think you could try telling about it to your T, maybe kind of slowly step by step. T will definitely have like a million questions, but that's ok, he needs to find out the details. Because well, if T doesn't know the full picture, he can't help you.