i got it! its because the movie designs dont use humanoid like faces right? so they got to make it that we know when the bots are PO'd. hence happy face mode/battle face mode. which gets me to thinking, since if this is how the movie treat robot facial expression, what are other, non battle uses for brute mode faces? - arcee finds hot rod forgot to put the toilet seat down? brute mode face. - forgot to set the tivo for robobaywatch? brute mode face. - finds out you get to be a combiner but you form the crotch? brute face mode.