I wouldn't worry about it though. I think that pretty much most of fanpop would prefer a different nom d’utilisateur 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 toi 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 toi can't change it. The only way to make a new nom d’utilisateur is to make another fanpop account. Now toi can supprimer the one that toi have, but that's something that toi probably don't wanna do. If I were toi I would.
