This was not Julian Richings' (Crusty) first appearance in a Percy Jackson production. He also played the ferryman (aka Charon) in the 2010 movie.
After the encounter with Cerberus, Annabeth tells Grover that her father had a dog when she was younger. This is taken directly from the book when Annabeth used what she learned during her time in obedience school with that dog, along with a red rubber ball she picked up in Water World to distract Cerberus to get into the Underworld.
In this episode, Crusty's store was the entrance to the Underworld. However in the novel, after defeating him, the trio find directions to get to the actual entrance to the Underworld, D.O.A. Recording Studios.
The title of this episode is taken from chapter 19 of The Lightning Thief novel.
Hades offers Percy and Grover pomegranate juice. In mythology, his wife, Persephone, ate six pomegranate seeds which compelled her to return to the Underworld for six months out of every year.