I wouldn't worry about it though. I think that pretty much most of Fanpop would prefer a different Имя пользователя to the one they have now. I don't know that for a fact obviously, but I've come across a lot of peeople who want to change their username.
It's why so many people make new accounts, but I don't advise that Ты do that. Because you'll only lose everything you've done and have to start over. And tbh, no one's that bothered about your username.
No Ты can't change it. The only way to make a new Имя пользователя is to make another Fanpop account. Now Ты can Удалить the one that Ты have, but that's something that Ты probably don't wanna do. If I were Ты I would.