clipped from: discuss.fogcreek.com   
you have to slap non-technical people with a wet mackeral when you're making a subtle point to them

To the vast majority of people, if it looks like a program, it's a program.  The two possible responses are (a) Why doesn't it work?, and (b) Look practically finished - when will it be ready?  Tomorrow?

I've been in too many situations like people have already described, where you can't get the idea across that IT'S NOT A REAL PROGRAM.

To us, it's a no-brainer that a mock-up is just a pretty face with zero brains behind it.  But what metaphor could the non-technical user be given to make this distinction clear?

I suppose if they're literate enough, "Potemkin village" might work.

Maybe a "prop" for the theatrical?

A "poser" for the young?

A "Milli-Vanilli" for the middle-aged?