[drfuchs]

Pardon the "Snappy Answer...," but the NYTimes Sunday Crossword not only has Al Jaffee as the keystone theme answer, but all the other main answers are humorous inventions in his comics that in fact became reality years later. In particular: Automatic Redial on telephones (1961), Spell Checkers ('67), Snowboarding ('65), Three-blade razors ('79), and Graffiti-proof Buildings ('82).

I haven't independently verified these, but I do recall other items that appeared as jokes in Mad, and later turned up for real: "Shpratz(sp?)", a spray to give your car the "new-car smell"; also an unnamed device that would keep your car from running if you weren't paying attention to the road (as depicted, for instance, because you were ogling someone you were passing on the sidewalk, though come to think of it, maybe it just snapped your head back to face forward).