Believing he is the only man capable of solving their problems, Dorothy and her friends travel to the Emerald City, the capital of Oz, to meet him.

Eventually, it is revealed that Oz is actually none of these things, but rather an ordinary conman from Omaha, Nebraska, who has been using elaborate magic tricks and props to make himself seem "great and powerful".

Working as a magician for a circus, he wrote OZ (the initials of his first two forenames, Oscar being his first, and Zoroaster being the first of his seven middle names) on the side of his hot air balloon for promotional purposes.

In The Marvelous Land of Oz, the Wizard is described as having usurped the throne of King Pastoria and handed over the baby princess to Mombi.

Oz explains that his real name is Oscar Zoroaster Phadrig Isaac Norman Henkle Emmannuel Ambroise Diggs.

He was played by actor Frank Morgan who also played several other roles in the movie including Professor Marvel (the mysterious traveling fortune-teller who Dorothy meets in Kansas with a horse named Sylvester), the Doorman at the Emerald City, the Guard at the Gates to the Wizard's Castle, and the Coachman whose transport is drawn by "The Horse of a Different Color".

Screenwriters Florence Ryerson and Edgar Allan Woolf created Professor Marvel for the Kansas sepia tone sequences.

The film centers on Oscar Diggs (portrayed by James Franco) and follows his journey from small-time magician to the ruler of the Land of Oz.

In it, he is portrayed as an overly flirtatious and overconfident con artist and stage magician who upon meeting Theodora (the future Wicked Witch of the West) and inadvertently sparking her obsession with him, is keen on fulfilling his role as the legendary Wizard destined to restore order to Oz (primarily due to the promise of the Oz Treasury).

However, throughout his journey and seeing the impact of his actions both good and bad, he comes to realize how much the people of Oz need him and devises a way to use his skill in illusions to free them, using his balloon to create the idea that he has been physically killed while hiding in a caravan so that he can use smoke and a makeshift cinema to project the illusion of his face, subsequently claiming that his "death" has simply allowed him to shed his mortal form.

The Wizard of Oz appears in the Once Upon a Time episodes "New York City Serenade", "A Curious Thing" and "Kansas" portrayed by Christopher Gorham.

Zelena leaves for the Enchanted Forest to seek out family, and she returns asking to go to the past so that she can change her own fate of being abandoned by her mother.

Angrily, she rips off the curtain and discovers his true persona is nothing but a simple man who likes orchestrating a false image to put on a good show.

Rather than become the new Witch of the West, Dorothy only wishes to go home; a desire Glinda grants by taking her back to see the Wizard, who is presumed to have reverted to his old form, since Zelena's magic has been undone.

During one romantic evening dinner, Walsh surprises Emma by hiding a ring on the platter of an ice cream sundae and then proposes to her.

Unable to sway her otherwise, Walsh's demeanor changes and he expresses knowledge of the potion Emma previously drank, which is what restored her memories.