So, I finished the Usagi Yojimbo Special Edition box set last night, which is all the stuff up to the Dark Horse releases. And yup, that was some enjoyable stuff. In particular, thewas a yeah holy crap, that was both really good and another strong reminder that despite the art this would totally not be suitable for children. Also a bit of a shame that the TMNT crossovers weren't a little more substantial/interesting, but oh well (also looks like maybe one is missing from these Usagi Yojimbo collections?) Which actually did cause me to realize that Usagi Yojimbo has actually held together a consistently released comic with tied together continuity for longer than the turtles, which is totally deserved but funny to think of considering the comparative popularity of the franchises (IE Usagi's just kind of gotten to be a hanger on of the TMNT as far as extended media goes).Seppuku ghost story
The TMNT crossovers are in the first Dark Horse collection. Unless you mean there are other crossovers before that which were skipped by Fantagraphics?