| A | B |
| Grover | keeper assigned to Percy |
| Percy Jackson | protagonist of the novel |
| Annabeth | Athena's daughter |
| Nancy Bobofit | ugly girl who picks on Grover |
| Gabe Ugliano | Percy's gross and smelly step-father |
| Ares | a biker dude who rides a Harley |
| Mr. Brunner | alias of Percy's Latin teacher |
| Mrs. Dodds | Percy's pre-algebra teacher |
| Chiron | trainer of great heroes |
| Mr. D | director of the camp |
| Clarisse | Percy turns the toilets on her and her gang |
| Luke | turns on Percy in the end |
| Chimera | this was a Chihuahua - at first |
| Echidna | the Chihuahua's owner |
| Argus | blond surfer dude in charge of camp security |
| Grover | wears the flying sneakers |
| Yancy Academy | the name of Percy's school when the book begins |
| Riptide | the name of Percy's sword |
| Charon | Security guard wearing an Italian silk suit at DOA Recording Studios |
| Kronos | Convinced Luke to steal the master bolt and helmet |