User blog:Really Big Hat/Unknown Person Running Around Here

Okay, I'm really ticked. There's this unregistered contributer running around here and erasing pages and putting inapropriate things on them like cussing and other stuff. They earased the Featured Characters Page wich I'm really mad about because I just put my character Juliette on there! And he/she erased some character named Adam and put inapropriate things on there to! What can we do to stop them?