Arnold is your stereotypical British villain. He came to Whispering Rock in order to enhance his skills, so he is better prepared to take over the world. He has his own religion (in which he is God) and he keeps trying to hand out explanatory pamphlets to convince people to join his cause.
He treats Dogan as an assistant (Dogan is not too clued up on this, he just likes the fact that Arnold isn't scared of him), and he has a fluffy white dog he's forever levitating around, because obviously, it can't walk.
He keeps trying to get Bobby Zilch to join his "evil team of evil" and he keeps bragging about owning a real-life paint ball gun. His favourite haunt is the main cabin area, where he tries to get free stuff from Cruller.