User blog comment:NickFusi0n/A Theory on The Coordinate and The Wall Titans/@comment-25358468-20140522214517/@comment-24930713-20140523211005

The beast titan can't be anyone that lives within the walls. Because the beast titan was unfamilar with the 3D manuever gear. So I'm guessing he's someone who's been around for a while. Although I am quite curious about their identity. All the "original" titan shifters shown so far appear humanlike while in titan form.(not including Ymir) So is it possible that the beast titan isn't human? Plus, Marcel is dead. o_O Otherwise Ymir would still be a "regular" titan. As for the titan that ate Eren. Eren didn't die when he was eaten. I think a titan shifter not only has to die, but the titan trying to eat them must consume the entire corpse. Hard to say for sure since the manga only shows Marcel about to get eaten.

I pretty much agree about the theory of the walls though. Considering the beast titan doesn't appear to be strong enough to break the walls down. And other "regular" titans don't seem capable of the climbing the walls. And Bertolt and Reiner seemed to purposly aim for the doors attached to the walls. Instead of attacking the walls directly.