Karen (called Shirley in the 4Kids dub) is Jim's pet crocodile. He considers her to be a part of his family and carries her around in a specially designed backpack. She is entirely devoted to Jim and normally does not let anyone else touch or feed her. She distrusts most people and growls or snarls when they approach her or Jim. However, when she met Judai, she ate out of his hand without hurting him, much to everyone's surprise.