Just an update: There have now been over 25 messages on the listserve yesterday and today about whether to list Geronimo Stilton as an Actual Author (as the books would have readers believe). Geronimo, if you're out there, your ears must be burning!
Apparently, using a fictitious person's name is legal. But 'authors' who can't write can't be used, according to The Rules. So, like, when those paintings done by Ruby (and others) are collected in a book, she can't be the author of the book.