Oscar Diggs is an elderly man and is the only known person in the city who has ever been resurrected via Ambrosia.
Dorian Gray visits Oscar from time to time, to purchase and sell gemstones, which are Oscar's interest. Oscar prefers to obtain emeralds, as they are his favorite gem. During one of Dorian's visits, Oscar admits he is green with envy over the youth that Dorian gets to enjoy, while Oscar is slowly withering away. Eventually, Oscar dies of old age. Dorian and Glinda later go to Oscar's house when they hide from Rose.
Gerda White is advised by Glinda to contact Oscar's spirit, to find a way to kill her stepdaughter Snow. Glinda summons Oscar's spirit in her magic mirror and asks him to bestow some of his wisdom. However, Oscar's only piece of advice is "Don't try to utilize something you don't understand". Oscar's spirit then leaves the magic mirror and kills Gerda, sapping her of all her psychic vitality, enough to strengthen Oscar's disembodied soul into a full-fledged ghost. Oscar's ghost then goes into Pepper Oni's household, where he eats the Ambrosia she has successfully managed to obtain, and is resurrected.
- Oscar is based on the Wizard of Oz from the story The Wonderful Wizard of Oz.