I had an imaginary friend named JoAnn. According to my parents, I started talking to and about JoAnn from the time I could first string sentences together. She looked a lot like me only a little older, she always wore a green dress with a white collar, and her hair was in long curls. Mom kept mine cut short. I remember feeling quite annoyed with my parents for various transgressions - stepping on JoAnn, sitting on JoAnn, interrupting JoAnn, failing to offer JoAnn any dinner, etc. I can also recall playing outside or in my room for hours with JoAnn, perfectly happy in our imaginary world.
Details of JoAnn are now somewhat vague. She slipped out of my awareness around kindergarten. Endless teasing by my family probably encouraged the disconnect (they still tease me about it 40 years later).
A couple of notes - I'm the oldest, was an only child the first four years of my life and my parents were busy professionals. For what that's worth in the creation of imaginary friends. The second thing I find interesting is I didn't know anyone named JoAnn. There was no one in my world, as a very small child, that went by that name. So where'd I get it?
I still talk to myself and have all my life. It may be inaudible at times but rest assured, there's a running commentary in my head at all times. Maybe she's still around!