The conception of the type in my head doesn't require extravagant physical and behavior mannerisms - I think there's sort of a stoic-to-permanent-temper-tantrum continuum here, with Hitsugaya on the far "stoic" end, Hiro and Elwood over on the other side, and Yahiko in the dead center. This is probably, in its turn, somehow determined by the stoic-to-spaz ratio of the male protagonist.

(Sasuke had juuust showed up where I stopped reading Samurai Deeper Kyo. I remember suspecting he was going to follow the type! I should start on that again...)