* When he first meets Annabeth: "She was wearing a leather jacket with a skull patch, ripped jeans, and combat boots. Maybe she thought she was in a biker gang, but she wasn't pulling it off." This shows his dry wit and how he doesn't take things too seriously.
* When he talks about the "Gorgon sisters": "The three of them were ugly. Real ugly. Even for monsters." He uses sarcasm to lighten the mood in a tense situation.
* When he is accused of stealing Zeus' lightning bolt: "Well, I'm not sure I'm ready to be Zeus' new favorite son. He seems kind of touchy." This shows his wry sense of humor even when facing serious accusations.
* When he meets Grover: "I knew it was Grover, even though he looked more like a giant squirrel than a satyr. He had brown fur, a shaggy, bushy tail, and a face that looked like a squirrel that had been kicked by a mule." This shows his ability to use humor to cope with the strange and bizarre situations he finds himself in.
* When he first meets Luke: "Oh, you're a son of Hermes, are you? That explains the kleptomania." This shows his ability to make quick, witty remarks.
Percy's sarcasm is often used to deflect his anxieties, to show his quick thinking, and to make light of even the most serious situations. It's a part of his personality that helps him cope with the challenges he faces, and it also makes him a more relatable and likeable character.