Arnie Cunningham is a fictional character from the novel "Christine," written by Stephen King. He is a high school student who becomes obsessed with a 1958 Plymouth Fury named Christine, which he restores and modifies. As Arnie's attachment to the car grows, he begins to change, becoming more aggressive and withdrawn from his friends and family. Throughout the story, Arnie's relationship with Christine leads to a series of violent events. The car seems to have a life of its own, influencing Arnie's behavior and decisions. This transformation highlights themes of obsession and the impact of material possessions on personal identity.