I think it's inevitable to put a little piece of you into your charries. They're a part of you and many of us became particularly attached to one or two of them. Most of my charries like Adi and Megan have my bouncy, friendly, easy- going, laid back traits. Everyone who knows me will notice this. Connor and Regina have the side of me that's sarcastic and wary of other humans. Kay, Rachel and Lucas are the ones very interested in knowledge. Zach is the shy side of me. These are just a few examples.
Also, there are charries that are unlike me. Anita, the one interested in fashion. I dislike that kind of stuff. What motivates me to play her is the fact that I like to learn about the various traits of persons; what makes someone who they are. Research plays a big part in this but as I RP her more (and other charries unlike myself), they speak to you easily.
In general, however a charrie may turn out to be, it's all interesting because RPing is something fun. Charries have varying personalities just like any of us RL peeps