I also got interested in symmetrical Venn diagrams with more than three sets. I learned that one can make an interesting looking five-sided one. Then I was thinking of something that I could do that would fill in a good number of the available spaces in the diagram, and again I thought of the Hitchhiker's Guide to the Galaxy, which conveniently has five major characters that interact in different combinations. Here is a rough attempt at showing when each combination of character was together in a location at the same time:
*Edit: 8/21/2015: Updated both charts. There was a minor error in both, regarding the fact that Ford Prefect left Arthur and Fenchurch before they rendezvoused with Marvin at the Quentulus Quazgar Mountains.
*Edit 9/27/2015: Changed things a bit in the timeline to show Trillian closer to Arthur near the beginning, per mathmannix's good suggestion. Also put a bit more detail around the part of the timeline around the "Hactar" event.
I should have seen that issue! Thanks for the suggestion! 
