These characters represent me in some way.  Within my own little multiverse of characters my sonas are basically gods.

Rusty is my main sona and represents me as a whole.  Rusty is not a character, they are an icon for me and my accounts.
Grin represents my mental state, usually being a stand in for depression and anxiety.  They also serve as a protector of everyone else, even though his reactions may be harmful in the long run.
Mimi represents the source of creative ideas.
CharChar represents my childhood.