User blog comment:Llama919/Possible Beast Titan Identity?/@comment-5774380-20150618200119/@comment-5774380-20150619024108

It seems that facts need to be twisted to fit with this theory, and when that happens that's commonly a signal that such theory is not the correct answer.

In order to make this hypothesis work we need to assume that Erwin's father didn't die but faked his death; that he somehow escaped from the dungeon, left the Walls and managed to survive alone in the lost territory (something impossible for what we know); that he became evil; and that the words the Beast Titan said to Mike should be disregarded because were all jokes. Almost everything we know about both characters need to be twisted in order to fit with the theory just because they have similar appearances -and that depends of the panel, because in the picture I posted here, Erwin's father doesn't look much like the Beast Titan-.

Obviously if we try to find explanations to support these facts we will end up finding something (even the most improbable things can be made look like possible with enough imagination), but I think the real probabilities for this theory to be true are very very few, and the most plausible explanation is that the Beast Titan is an inhabitant from the Homeland not yet introduced and with little to no contact with the civilization of the Walls; at least until he experimented with the people of Ragako to test humanity's strength as Ymir guessed, and to take some "souvenirs" with him.