I am traumogenic (trauma created/clinical DID) plural system. It is highly likely that I never had a "core personality" that I was born as and instead have always had either an infant mental state or multiple personalities. (During the time most babies begin to form a coherent personality, I formed several. It is possible that not every system forms like this but highly like I did)
Every time I've felt I was singular, I've experienced mental walls, amnesia and other DID symptoms. If someone could do a "I'm singular ama" that'd be cool because I have questions too. :)
Did you by any chance watch United States of Tara?
No. I had actually known about about the idea of plurality for years before I came to terms with things. I had fiercely rejected the notion of plurality being real on favor of explanations centered around the notion of being psychic. The other members in my system are actually vital to my functioning. If I blocked them out entirely, I'd falter. I think I personally require healthy religious ritual and engage to be self actualized but the advice the alters were giving was mundane.
I had an existing clinical history of CPTSD and body dsymorphia. Whenever people mentioned that I might be a system, I'd panic. I'd often have experiences of being having an alter take over to do a task or stand up for me. It was scary but they actually often made things safer/better for me and those around me. (Like walking me out of a room when I felt so triggered I was going to yell)
My experience of being a system was very different from what I was seeing in media and on tumblr. I could see the alters as being different versions of me. Also I was utterly fascinated by theorists who wrote about things that reminded me of plurality despite being in fierce denial. I had a professor think it was cool to tell me he thought I was a system. I felt so panicked after me and so unsafe. I'm one of the front people, we can be afraid of alters not because they are dangerous/bad but because we were initially created by the mind to deal to allow the entire system to live while the other alters who held the trauma memories went into the background. To us, when we are not working on our recovery, we can be very scared of the others in a system.
I had friends comment on my rapid but covert enegry level/style switching, mannerism changes, etc. Alters in a DID system will often pretend to be the host but without full context about how we live our lives. United States of Tara is not the case for a wide number of system. Her family is actually largely functional while she pretends extremely severe symptoms. I've only read a bit about the show. As a host who has been in fierce denial of the system, when I heard of that show my response was "No, that's fake, rather not. Gross, why are they misleading people who are probably just psychic? Bye"