"He's good-looking but don't you dare tell him I said that." --Annabeth Chase about Percy. :)Percy is described as a very handsome young man, with jet black hair and bright sea green eyes. Despite most assuming he is tall, this has never been confirmed. He had a gray streak of hair he obtained in The Titan's Curse from holding the sky, but has since lost it, as stated in The Mark of Athena by his girlfriend. At the beginning of the series, Percy was average in athletics but later from his training, becomes very fit, muscular, and lean. He does not seem to know it, or may simply refuse to acknowledge it, but a great number of girls find him extremely attractive.
After he slew Polybotes in The Son of Neptune, Percy received a tattoo of a trident and SPQR on the underside of his arm. Annabeth (his girlfriend) says that Percy grew even more handsome, muscular, taller, and that his lips are salty. According to Piper (a friend), he smells like the sea, looks like a skater and a troublemaker, but she can still see what women would like about him, even if he isn't her type. Piper later states that when Percy pleads, his sea-green eyes seemed to be "like a cute baby seal that needed help," and wonders how Annabeth ever won an argument with him.
Percy is a very caring and loving person. He is kind, funny and sarcastic. Apparently, his fatal flaw is excessive personal loyalty. Meaning he would risk the world and even his own life to save a loved one or even a stranger.
ADHD: Percy's supernatural alertness and keen senses that keep him ready for, and alive, in battle. It also lets him analyze his opponents fighting style as well as pick up minor details about an opponent, such as where their muscles tense so he can tell which direction they'll attack from. This is one general trait of demigods.
Dyslexia: Percy's brain is "hard-wired" for reading divine Ancient Greek instead of mortal languages. During his time at Camp Jupiter he learned to understand, and possibly speak, Latin to an unknown degree. This, along with ADHD, is a trait common to most demigods.
Fighting Skills: Percy is a naturally talented and expert swordsman, capable of holding his own against and even defeating larger, more experienced, and more powerful opponents, including gods and Titans as well as monsters. In The Son of Neptune, even after losing the Curse of Achilles, he is still shown to be able to fend off an entire army of continually resurrecting ghosts by himself while still protecting Frank (a friend). His Greek training and unpredictable, solo fighting style make him particularly dangerous to the demigods of Camp Jupiter, who are used to fighting as a group, allowing him to easily defeat multiple opponents at once.
Curse of Achilles: (formerly) After bathing in the River Styx, Percy was given supernaturally superior speed and strength as well as invulnerability except for his vital spot opposite of the navel. With the Curse of Achilles, Percy's own combat skills are enhanced to the point where he can single-handedly defeat entire armies as well as gods like Hades and Titans like Hyperion (albeit he had some help in defeating Hyperion). He later loses it by touching the Tiber river as it was a Greek blessing and he could not enter Roman territory with the curse.