It's really hard to tell that you're multiple. The theoretical "big-bang" of the so-called disorder is to have an alternative method of mental functioning while protecting parts of one's self (core, id, ego, whatever...). In each individual, there is a different way of expressing it, and it may evolve quite differently over the years, but the basic fact of the matter is that one of the people your multiplicity is hiding from is yourself(s).
This leads to a conundrum for people who are multiple and don't know it (yet), where they can "hold it all together" quite fine, and don't usually exhibit behaviors that are overt until or unless their secretive innards stop working like a well-oiled machine. They can go to their grave never knowing they were multiples, and that's all well and good because after all, ignorance can be bliss.
Those of us who have, through inability to function or through happenstance or deep inner delving, found out that we're multiple can have moments we are more aware of our multiplicity than others. I can go days or weeks at a time where it matters little to not-at-all that I am multiple.
Then there are other days, usually days where I get fed up with running on autopilot, days where I want to feel 100% of everything going on in my head, body, heart & soul, that I'm aware of everything going on in my head.
Multiple moments are something else again. One can be in any of these states of being: blissfully ignorant, auto-pilot, fully diversified in all your manic glory, and experience a multiple moment. For me it's usually going back through things I've written, photos I've taken, or artwork I've drawn. The dual knowledge that I created something -- it was my hand, my pen, my pencils, and the absolute conviction that it was not ME, that it was not my will what drove the hand, my inner voice that created the poem or narrative. Moments like these, it's like suddenly looking into a mirror and other people in my head are staring back at "me" (whatever THAT is). This is a multiple moment.
Another multiple moment happens at times when someone asks me a question and 3 voices answer. "What would you like for dinner?" "Pasta. No, peanut butter and jelly. But make it with meatballs." Or "Do you like that song?" "Yeah, it's ok. I don't like the singer. I love it." Well, these are poor examples, but you get the idea. You get these types of answers when I'm distracted usually.
Multiple moments are one of the times that multiplicity is overt, if still subjective. I'll be sure to post one if I "have a multiple moment".