As the son of Greek god Poseidon and mortal Sally Jackson, Percy is a powerful demigod, or half-blood. For a long time, Percy believes himself to be a normal kid who cannot manage to stay in one school without finding trouble, but eventually finds out the truth about who, and what, he really is. As a half-blood, Percy is constantly put in danger by the monsters that many people believe to be mythical, like a Minotaur or a Cyclops. Percy spends each summer at Camp Half-Blood where he and his fellow half-bloods, or heroes, train to fight the monsters that threaten themselves and mortals. Once in a while, though, some heroes obtain quests where they have to go and accomplish the dangerous task. Because Percy's father is such a powerful god, Percy is catapulted into going on a quest every summer that he is at camp. In The Titan's Curse, it is Percy's third summer at Camp Half-Blood and he again is assigned a quest that he must complete. With the help of his friends, Percy can always manage to get out of his tough situations and also gets help from his father, Poseidon.
Grover Underwood is not only a satyr, half-human and half-goat, but he is Percy Jackson's best friend. Before Percy knew that he was a demigod, Grover was his friend and protector at boarding school. Finally when Percy is attacked by a teacher, Grover is the one who tells Percy who he is. Ever since, Percy and Grover have been great friends. As a satyr, Grover's life goal is to find Pan, the god of the wild. In order to be able to look for Pan, Grover needs a searcher's license, which he can only obtain by successfully helping a half-blood to safety or by proving himself in a quest. Because Grover lost Percy when he was first bringing him to Camp Half-Blood, he needed to go on a quest to pass the test. Eventually, in The Lightning Thief, Grover manages to help complete a quest and get his searcher's license. After getting his license, Grover went off searching for Pan and only returned to Camp Half-Blood when Percy saved him from a Cyclops in The Sea of Monsters. What with searching for Pan, finding new half-bloods, and being at Camp Half-Blood, Grover is never a calm or relaxed satyr.
Annabeth Chase is a demigod, just like Percy Jackson. She too is a camper at Camp Half-Blood. When Percy first got to camp, she nursed him back to health, then showed him the ropes of camp. Annabeth immediately became Percy's best half-blood friend. Unlike Percy who is a son of Poseidon, Annabeth's mother is Athena, the goddess of heroes. Her father is Frederick Chase, who later married and gave Annabeth a stepmom. When Annabeth was young, she felt her father and stepmother hated her and so she ran away where she met Luke and Thalia, two other demigods, and Grover. Together, they fought for their lives and eventually made it to Camp Half-Blood. Later, in The Titan's Curse, when she is in danger from Kronos, the Titan Lord, she finds out that her father and stepfamily care deeply for her when her father comes and fights for her life.
As another half-blood, Thalia, last name unknown, is the daughter of Zeus. Before Percy even knew that he was a demigod, Thalia, Annabeth, Luke, and Grover made their way to Camp Half-Blood. As the group approached the camp, they were attacked and Thalia gave her life so that Annabeth, Luke, and Grover could be safe. Ever since Percy has been at camp, the tree guarding the camp from monsters is known as Thalia's Tree because her spirit was captured inside it. At the end of The Sea of Monsters, Thalia's Tree was cured with the Golden Fleece. When the tree was cured, Thalia was brought back to life as the punk-rock teenager that she is. Afterwards, Thalia, Annabeth, and Percy became great friends and later in The Titan's Curse, when Annabeth is captured by Luke and Kronos, Thalia and Percy go across the country and riske their lives for her.
***Photos of characters either taken from The Lightning Thief movie cast or chosen based on personality and features.