Nearly a century ago, a pair of American inventors packaged sticks of oily chalk in a green and yellow box and instantly created a sensation--some might even call it the Chicken Dance Elmo of its day. More than 100 billion Crayola crayons have been produced since Harold Smith and Edward Binney first spotted the need for kid-friendly coloring tools.

The Toy Industry of America, which keeps track of the most popular toys, measures by the number of units sold and by the dollars spent on them. They also rank the most popular toys introduced in any given year.

As recently as a couple of months ago, crayons still made the top-ten list for most popular toys sold in the United States--at least when measured by units sold. If you measure by cost, crayons fall off the list because they're so much cheaper than the average modern plaything. The same is true for Play-Doh and Matchbox cars. These are the toys many of us grew up with, and chances are they will still be around by the time our kids have children.

Chicken Dance Elmo, a toy that sounds a little like a bad joke but actually was introduced in May 2002, is one of this season's hottest products. So are Rapunzel Barbie and Holiday Barbie. And so is something I'd never heard of: a card game called Yu-Gi-Oh!.

This got me wondering: What made crayons remain popular for almost a century, and what are the chances that Chicken Dance Elmo and Yu-Gi-Oh! will still be selling like hotcakes in the year 2102?