"We shall see the crumbs of bread... and they will show us our way home again." - Hansel and Gretel
"Organ Grinder" is based on Hansel and Gretel, a well-known German fairy tale originally published by the Brothers Grimm in 1812. When a young brother and sister, Hansel and Gretel, wander into the woods, they take a slice of bread and leave a trail of crumbs to follow home. However, they find that the birds have eaten the crumbs, and they are lost in the woods. Similarly in "Organ Grinder," the brother and sister vagrant teens leave a trail of puka shells when they're dragged into the forest to have their organs harvested by the Geiers.
In the original tale, the children come across a gingerbread house, where a cannibalistic witch lures them inside with the promise of soft beds and delicious food. Similarly, the homeless teens in "Organ Grinder" are lured into a white van with the promise of a stable job. In both stories, the enemy seeks to kill their captives; the witch intends to eat the children, while the Geiers intend to harvest their victims to sell their organs on the Wesen black market. Also in both tales, the children are left homeless because of their parents. Likewise, near the end of the episode, while Nick fights Dr. Levine, now in Geier form, she ends up falling into a fire pit used to burn the dead bodies of the harvested. This greatly parallels the witch in Hansel and Gretel who is thrown into her own oven, and burned alive.
"Still, after a short time the family's distress again worsened, and there was no relief anywhere in sight."