Fun to play with, not to eat.

Play-Doh Brand Modelling Compound began life in 1927¹ as a substance for getting soot off of wallpaper. For some time, housewives had been rubbing a homemade goop against the walls to clean them.  I guess the soot had a tendency to stick to it more than to the walls?  Naturally, companies began selling premade mixes of the stuff.  Sadly for the manufacturers, though, the increased use of electric appliances was doing an even better job of removing the soot from the walls of homeowners.  By the mid 1950s, the manufacturers were practically broke.

But in an unexpected reversal of their reversal of fortunes, some of their compound fell into the hands of some Cincinnati schoolchildren. After the shrieking died down, the adults realized that if they removed all of the horrible poisonous cleansing chemicals (boric acid, mostly) from the stuff, and add some friendly dyes, they could market it all over again as a plaything!  You still shouldn't eat it, though, even if it does have a "subtle almond scent."¹

¹http://books.google.com/books?id=jftapGDTmYUC&pg=PA115#v=onepage&q&f=false