Jack Vance's scifi/fantasy classic "The Eyes of the Overworld" starts with a quest which has the protagonist steal magical eye glasses which make the denizens of a village who literally live drenched in shit and mud and eat garbage believe they are lords and ladies living in palaces and eating the most delicious foods.

They know it's not the truth, but for all intents and purposes, while wearing the magical eyeglasses it becomes the truth.

The rest of the book is hilarious and I fully recommend it.