The HBO Recycling Program is a visualization by Craig Robinson that shows many of the actors and actresses that HBO has used in multiple series. This was posted as part of an article on Grantland.com.
Actors who have appeared in three or more episodes of multiple scripted, live-action, original, HBO series since OZ (excluding miniseries).
Click on two shows, and the interactive version will highlight only those actors in both shows.
Zack’s interactive infographic is made with PaperJS, underscore.js, and a little JQuery. He has made the code open source, and it can be used to display the connections between other groups as well, if anyone has the motivation to map their own connections.