01 Go watch The Wizard of Oz (Victor Fleming, 1939, MGM). Only then, get some more popcorn and read the seminal publication on Wizard of Oz techniques in design: Kelley, J. F. (1984). “An Iterative Design Methodology for User-friendly Natural Language Office Information Applications.” ACM Transactions on Information Systems (TOIS), 2(1), 26-41.
In Wizard of Oz techniques, the responses from people, devices, apps, or the context/environment are manually created by invisible operators (“wizards”) behind the scenes. The users are working under the assumption that they are dealing with an actual working prototype. Wizard of Oz approaches can help to efficiently test user reactions before investing time and effort into more complex working prototypes.  All relevant parts of the service or system are carefully prepared and rigged to allow the “wizards” to create realistic responses on the spot. Think of the operator as an invisible puppeteer for those objects and service elements, simulating the operation of backstage processes, devices, or the environment. The core functionality and value are explored and evaluated.