Smoke and mirrors
Smoke and mirrors in programming is used to describe a program or functionality that doesn't exist yet, but appears as though it does. The source of the name is based on magicians' illusions, where magicians use smoke and mirrors to accomplish illusions such as making objects disappear, when they really don't disappear at all. In programming, this is often done to demonstrate what a resulting project will function/look like after the code is complete.
Smoke and mirrors is not recommended when displaying any program, as it can lead to expectations for an impossible or extremely difficult task that was not apparent from the outset.
Columnist Jimmy Breslin is credited with popularizing the phrase.