In Percy Jackson And The Lightning Thief, how does Percy explain why he went to the Garden Gnome Emporium?

In Chapter 11, Percy enters Aunty Em's Garden Gnome Emporium because he can smell the scent of hamburgers coming from the curio shop. He remembers how hungry he is and how he misses the taste of fried foods and double-cheese hamburgers; the only kind of food he gets to eat at Camp Half-Blood are healthy 'grapes, bread, cheese, and extra-lean-cut-nymph prepared barbecue.'

While Percy and Annabeth are enthusiastic about checking out the place, Grover is wary of what he sees. There are statues of humans, satyrs, and all kinds of animals in the front lot. Meanwhile, the trio are greeted by Aunty Em, who invites them in. She is wearing a long robe, and her head is covered. Aunty Em offers to cook for them after she hears that they are all orphans. Before long, she emerges with plastic trays heaped with double cheeseburgers, fries, and vanilla shakes. The trio are in fast-food heaven.

However, Percy can't help noticing that the entire warehouse is filled with statues of people in different, strange poses. Aunty Em says that some of her statues are marred, as it is difficult to get the faces to come out right. Soon, she tells the trio that a jealous woman once tried to separate her from her boyfriend. Accordingly, her two sisters stayed loyal to her, but they have since passed away. On hearing this, Annabeth becomes uneasy. Now, she and Grover want to leave immediately; Percy, on the other hand, feels so full and contented that he wants to stay a little bit longer.

In due time, Aunty Em wants the three friends to pose for a picture. However, everyone notice that she has no camera in sight. When she reaches up to her head to remove her head-dress, Annabeth suddenly realizes who she really is and manages to warn Percy and Grover in the nick of time. She shouts at them to look away from Aunty Em's face. Aunty Em, after all, is Medusa.

As Medusa unveils herself to the trio, she reveals that Annabeth's mother, Athena, turned her into a monster when she found Poseidon and her in Athena's sacred temple; this is why Medusa has snakes for hair. In the meantime, Grover tries to attack Medusa with a tree branch, but Annabeth tells Percy that their only chance of survival is for Percy to cut off Medusa's head.

In the end, Percy manages to get close enough to lop off Medusa's head by approaching her with the aid of a green gazing ball. After Annabeth covers up Medusa's head with black cloth, Percy packs the head into a box to be mailed to the gods at Mount Olympus at their address in New York City.