Athena was a maiden goddess (she could never marry) yet she had children such as Annabeth because like herself her children are born from pure thought and given as a gift to the men she truly admires therefore she is able to have demigod children and still be a maiden goddess
When in the Parthenon Museum, Annabeth begins telling Percy a story about her mother, Athena. The story she tells is the Greek myth about how the capital city Athens got its name. The citizens of the city were arguing over which god to name the city after. The two choices were Athena and Poseidon, Percy's father. Both agreed that they would bestow a gift onto the town, and whichever gift was deemed more useful, that giver would have the town named after them. Poseidon stuck his trident into the ground, and created a spring, which the townspeople could use the water from. Unfortunately, the water turned out to be too salty and therefore useless. Athena presented a single olive tree. The people realized the tree had many uses: Its fruit for eating, its wood for building and burning, the oil from its fruit for cooking and for bathing, and the pits of the olives could be planted, therefore bringing up more olive trees. The people agreed the olive tree was more useful, and therefore named the city "Athens", in honor of Athena.
In Greek Mythology, Medusa was turned into a Gorgon when Poseidon, Percy's father, raped Medusa in the temple of Athena. Athena, Annabeth's mother, took offense and cursed her. Hence, Medusa's hatred for them, and her reference to unfinished business.
When Chiron is calling for the campers to gather around to go over the rules for Capture the Flag, he yells for Dylan and Paris to stop "lollygagging". Chiron is played by Pierce Brosnan, whose two younger sons are named Dylan and Paris.
In Greek mythology, the goddess Athena is a symbol of virginity. She never had any children. But in the books, it is said that Athena would create the children using her mind, being the goddess of wisdom. Adding in the traits of the father of the child and adding in some of her own.
Uma Thurman, who plays Medusa, interacted with a number of live snakes with the help of a snake wrangler in preparation for her role. Handling and holding snakes, she said, helped her imagine how it might feel for Medusa to have live snakes sprouting from her head.
In the Greek Myths, Persephone was abducted by Hades into the Underworld, but Zeus demanded her return on earth. However Hades tricked her into eating pomegranate seeds and was forced to stay in the Underworld during the winter months and returning to earth the rest of the year. However in the film, Percy Jackson had 10 more days until the summer solstice to return Zeus' master bolt and during the time Persephone was seen in the Underworld at summertime.
In the book, there's a character at Yancy Academy named Nancy Bobofit. She is described as having red hair, pale skin, and freckles. A girl matching this description is seen in the background when Percy and his classmates are at the museum.
The hydra Percy faces in the Parthenon Museum in Nashville was a creature in Greek mythology. It was the offspring of Echidna and Typhon. The Greek hero Heracles (known more commonly by his Roman name, "Hercules") defeated the hydra by cutting off most of the heads, save for the one immortal head, having his nephew cauterize the wounds with a burning torch, and burying the remaining head with a large boulder.
When Percy, Annabeth and Grover meet Persephone and the hellhounds, Persephone tells the hounds "fige" and "makria tous" this is Greek for 'leave/go' and 'away' from them respectively. Also when she calls the hounds back "ella tho" meaning 'come here', also in Greek.
In the book the obstacles Percy, Annebeth and Grover face are a fire caused by Furies, being tricked by Medusa, escaping the St.Louis arc, escaping a trap made by Hepheastus, and getting out of the Lotus hotel/ casino. In the movie the obstacles they face are escaping Medusa's lair, killing a hydra, and breaking out of the Lotus hotel/ casino.
There are major changes from the book in the movie: Percy gets the pearls from a sea nymph in the book but gets them by traveling all around the US in the movie. In the book, there is a fight scene with Enchinda and a Chimera. This is deleted in the movie. The pantheon isn't in the book. Sally took Medusa head and stoned Gabe, selling the statue. Instead he opens the fridge and Crumbles to pieces. There are many other changes.