I missed the whole DUPLO thing as a kid. Instead I had something called Bristle Blocks, which may sound like a horrible intestinal ailment, but they were actually multi colored bricks that locked together in a more free form way. Really cool. When I got to old for the Bristles, my family started buying me LEGO, all of which I still have today. Best toy investment a parent can make.
I am sorry Mrs. Smith, but your child has a full blown case of the Bristle Blocks.