Have you ever created a self-insert character?

[Red]

Yes, a man who makes big mistakes by small and simple choises, like me.
He narrates the whole story from his point of view, and only appears at the beginning and at the end of the plot. He's the one who allowed this problem to happen, responsible for the entire story the novella is telling about.
In addition, there's one character who's identical to me. Shy, has red hair, misunderstand things easily, likes to think, silent. His actions are like mine, without knowing about things he's not aware of, of course.

[Mechavomit]

When I was 15-ish, me and my friend were working on an RP/fanfic thing and I created a shameless self-insert character to hang out with my favourite canonical character (yes, I know...).
However, that character evolved with time and turned into something completely different and a lot more complex. I changed her age, personality and added pretty nice character development without realising it. Her arc ended up as the focus of the entire story and it worked pretty well.