Usagi Yojimbo DojoBoard

Is there a complete listing of guest appearances that other people's characters have made in UY? The "Other Comicbook Characters by Stan Sakai" page lists some of them, like the Groo cameo in one of the first Albedo stories, the TMNT cameos, and the cameo by characters from Akiko in DH #28, but the Calvin and Hobbes cameo (which I found a little bit strange) in "The Tower" (Fantagraphics Vol. 3) isn't on the list. Are there any more guest appearances that aren't listed here?

While we're on the subject, I'd love to see Steve Purcell's Sam & Max make a UY cameo appearance (a few of their adventures have involved time travel, so it doesn't seem like it would be that great of a stretch).

http://telltalegames.com/samandmax/