Board Thread:Theories/@comment-27938131-20161216095442/@comment-30455198-20161220094729

CommonSwift wrote: My guess is the type of serum decides the body type of the titan or else the Wall titan wouldn't look like the Colossal.

Rod said he had chosen a fighting type for Historia, so I am guessing Armin's titan will look like Annie's and Eren's. Well, I think the main ability always get transferred, and then the mindless Titan's ability also gets transferred as a bonus.