For me, I denied I had any type of "multiple personality disorder" even after a college T said he thought I had it. I just thought I was forgetting things and people. Even though I had my "friends" inside my head, I didn't know they could just "take over" and control "my" body.
Sometimes I would start getting into it with a roomy and then I would be blank - just not there - but would "snap to" and be eating out somewhere sitting at a table and I had no idea where I was... not just what restraunt, but what STATE! Also, at college I would have people come up to me and ask how I was doing and start talking to me like they were my best friend. I would just look at them without a CLUE as to who they were. They would stop and ask me if I was so and so (they actually were using my middle name which one alter uses) but no one knew that about me (or so I thought!). Then they would dismiss themselves with an apology and tell me I had a twin running around campus.