Who is Stanley Yelnats?

Stanley Yelnats—also known as "Caveman"—is the protagonist of Holes. He seems to have inherited the family gene of bad luck, because try as he might, he just can't catch a break. Overweight and lonely, Stanley's an object of fun for class bullies like Derrick Dunne, who picks on him relentlessly.
In keeping with his run of bad luck, Stanley ends up taking the rap for a crime he didn't commit and is sent to the notorious Camp Green Lake, a detention center for juvenile delinquents. The camp's regime is supposed to be run on tough love principles, but in reality there's a whole lot of tough, and not much in the way of love at this terrible place. As part of their punishment, Stanley and the other boys are forced by the sadistic Warden—the poison nail-varnish-wearing Ms. Walker—to dig holes, a soul-destroying task that everyone hates.
However, the time that Stanley spends at the camp isn't a total dead loss. Much to his surprise, it proves to be quite an educational experience for him. Not only does he gain in self-confidence, he also finds out a lot about his ancestors, and in the process is finally able to lift the Yelnat family curse.
More information about Stanley and the other characters in Holes can be found in the link below.