Ooooookay, so I finally got around to checking my guides today. "Anatomy of Mr. Saturn" comes from the マザー2のすべて (Everything of MOTHER 2) guide book. http://earthboundcentral.com/merchandis ... gy-guides/
Ha ha. Apparently Mato already knew this was the guide with the anatomy pages, per his description of the guide book:
Similar to everything of MOTHER. This one tells you how to finish MOTHER 2 in 24 hours. It's also packed with info and theories about the Mr. Saturns, including a gross anatomy pic.
Anyway, I took pictures of the pages that talk about Mr. Saturn: http://gallery.me.com/mspotter#100012
Mato or someone else can probably give a brief overview about what it's saying about Mr. Saturn, but according to the picture, apparently Mr. Saturns get all disoriented and confused when you pick them up by their heads and hold them upside-down!