When introducing graph modular decomposition, most authors use the 11-vertex graph, which I copy from wikipedia.
The question is who is (are) the original designer of it. (I'm not asking who drew this graph for wikipedia, but the original source of it.)
The wikipedia page was created in December 2006. The earliest source I can find is the Habilitation thesis of Christophe Paul dated on May 17, 2006. (I didn't search intensively.)