I think the Theiss example is a good one. On the other hand, you can make SOME logical extrapolation. In the Lost in Space thread I mentioned that touch-tone dialing had been introduced two years before the aforementioned episode was made, and just having all the phones touch-tone would have made things look more futuristic than they did. Likewise, rent one or two custom cars from Gene Winfield or someone and park them on the street. Anything to blur the edges of "now" off the show.