There is a contention that the Wolverine & The X-Men (W&tX) animated series and the Avengers: Earth's Mightiest Heroes (AEMH) animated series share the same universe. There are three things offered as indicative of this:
* Christopher Yost indicated that they were in a chat log.
* The voice actor who performed the voice of Nick Fury is the same.
* The MRD, mentioned by Nick Fury in one of the micro-episodes, was invented in the W&tX series.
The most powerful argument for me is the first; that Christopher Yost, who serves as the Story Editor for AEMH indicated that they would share a common universe. However, that was back before the W&tX series was officially canceled; if the two series were both running, then such a cross-marketing synergy would have made sense. Once the W&tX series was canceled, however, it made no sense at all; why limit your use of roughly 1/3 of Marvel's characters by adhering to the W&tX series continuity when there was no upside?
The two series sharing a voice actor is not proof of anything. There are a handful of actors who are very popular in the hero adventure animation world. Fred Tatasciore (http://www.imdb.com/name/nm0851317/ ) has played numerous characters in the Marvel and DC animated features, including the Hulk in the Lionsgate Hulk VS features, and a video game; that he has played the character in several venues does not mean those venues share a common continuity with the AEMH.
Further, while the same voice actor may have played Fury in both shows, the appearance of the two characters is quite different, including having eyepatches over different eyes!
The appearance of the MRD is categorically not proof. It was created for the W&tX show, but was introduced to the mainstream MU via X-Factor, 204-206 (June 2010) or so, by Peter David. Arguing that its proof is just the same as arguing that Batman: Brave and the Bold is the same universe as B:TAS because Harley Quinn first appeared in one, then the DCU, then B:B&B.
Don't get me wrong - While I think it would be a bad idea because of the differences in "age" of the MU (AEMH seems to be set in modern times but with the MU begining framework) and the W&tX, as well as putting unnecessary restraints on the writing team, I'd have no serious complaint about it as such; but saying/wishing it so doesn't make it so.
Until there is an appearance unique to both shows, all one can show is intention, and speculation - neither is proof. If the W&tX show is meant to share the continuity, we shall at some point be provided with such proof - but we have not yet been.