1: they start out based on another series/fandom, or even just things I see in real life or on TV, but slowly start changing and becoming more and more original that you can no longer tell.
2: well, my first OC started to get a little 'lonely' so I started making a backstory then making more characters and now there's a whole story around them that hopefully one day I will be able to finally make the comic ;A;
3: the freedom, I just love making things the way I want them to be. they all come out exactly how I want them, not how anybody else does. They're mine to call my own and say, "hey! I made this character up myself."