I'll probably buy the first volume of TL-SC, before it becomes illegal for Ken to sell it. It's obvious this series isn't going to go anywhere, but it would be at least somewhat interesting to experience a bit of it before it's gone.
Anyway, Athair is in Sonic Underground (albeit with a rather embarrassing design). I have to assume that he was created during the production of SatAM just as an idea, and that he later went on to be in Archie and SU from there. So I doubt Mike Gallagher owns the rights to him. (Then again, I'm not exactly sure what that means anymore. This copyright stuff is headache-inducing....)
Actually, I wouldn't say M:XYL violates the characters-never-get-old rule. That's what's always seemed so strange about it; it happens 25 years later, and Sonic doesn't seem to have aged a bit.
As for it screwing up the "present day" story, there was an off-panel about this. It went something like this:
Knuckles: Yeah, I've been enjoying living dangerously ever since I learned I'm still alive in "Mobius: 25 Years Later." You can't argue with the future.
Editor: Or it could be that M:25YL takes place in a possible timeline in an alternate universe.
Knuckles: *gulp*
[The Chaotix enter the room.]
Espio: Hey Knux, you ready to walk across busy streets?













