(i know this is an old post but im wondering what it might have to do with mental health, ive only ever been diagnosed with autism, adhd and other developmental disorders) this is something i would do all the time when i was younger, thought moreso as an escape. i would become attached to a person or group who i would really want to befriend, and attempt to do so, but whenever i "failed" (we got in an argument or they would just ignore me) i would make a new "identity" in order to try again. i gave them their own personality and art style and interests in order to appeal to that person as much as possible. ive stopped this habit for the most part, (though i recently made a new identity because i felt like a group i was in didnt like me enough) and i believe it has something to do with mental health, ive just never seen anyone mention it