Heh, 't'is' is just a fancy old style English way of saying 'it is'.
You're right, your brain cannot affect your facial features (though some profilers argue that psychology, 'your brain' can be judged by immediate biological distinctions, such as facial features), but in this case, I'm merely saying that certain shapes within your face look typical of eccentric types.
I'm merely suggesting you are!
Oh, and aren't appearances one of the greatest factors of eccentricity?
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Heh, dress and hair style esp-.