Rex "X-Ray" is a camper at Camp Green Lake in the film, Holes. He serves as the leader of D-tent.
X-Ray had a mixed personality. While he could be funny and kind, he could also be rather selfish and greedy. Examples of which include taking Stanley's bread from his dinner plate, and taking all the credit, plus the day off, when Stanley found a bullet (lipstick tube) with Kate Barlow's initials inscribed on it.